About 85% of the body's phosphorus is found in bones and teeth and is
combined with calcium. The rest of phosphorus is in the soft tissues . Phosphorus
in the blood exists as phosphate, which is necessary for the generation
of bony tissue; the metabolism of glucose, fats, and proteins; and the
storage and transfer of energy. The range of normal for adult phosphate
levels is significantly different than the range of normal for children. The
difference is partially attributed to the increased level of growth hormone
present in children until puberty.
Due to the relationship between calcium and phosphorus, blood phosphate
concentration is closely linked to plasma calcium. Increased phosphorus
levels are accompanied by a decrease in calcium and, conversely,
decreased phosphorus levels are accompanied by an increase in calcium.
Normal Range
Adults
2.7-4.5 mg/dl
Children
4.5-5.5 mg/dl
Blood Chemistry Tests (Part 1)
39
Variations from Normal. Hypopphosphatemia, increased phosphorus
level, is most commonly associated with kidney dysfunction as in renal insufficiency,
severe nephritis, and renal failure . Hypoparathyroidism, increased
growth hormone, vitamin D excess, bone tumors, and Addison's
disease also demonstrate increased phosphate concentrations . In most of
these situations, a decrease in plasma calcium is also present and diagnostically
significant .
Hypophosphatemia, decreased phosphorus level, is associated with
hyperparathyroidism, rickets in childhood, osteomalacia in adults, malabsorption
syndromes, malnutrition, and an excessive amount of insulin
in the body. Hypophosphatemia is accompanied by an increase in plasma
calcium.
Interfering Circumstances. A false increase in phosphate follows the use of
laxatives or enemas. Oral laxatives may increase phosphorus levels as much
as 5 mg/dL within a few hours. Destruction of red blood cells will also
cause hyperphosphatemia.
Dec 21, 2010
Bicarbonate (HCO,)
Bicarbonate plays an important role in the blood buffer system, which
helps maintain the normal blood pH of 7.4. Simply put, the blood buffer system
is activated by a buildup of positively charged hydrogen ions in the
body. When this buildup occurs, bicarbonate, a negatively charged ion,
combines with the hydrogen to produce a weak acid, or buffer, called carbonic
acid. After a series of chemical reactions, an equilibrium is established
and pH levels are held within the normal range. Variations in bicarbonate
concentrations will affect the pH levels in blood.
Bicarbonate also serves as a transport mechanism to move carbon dioxide
(CO2.) from the body tissues to the lungs where it is exhaled. Carbon
dioxide is a waste product and must be removed from the bloodstream .
Normal Range
22-26 mEq/L
Variations from Normal. Decreased bicarbonate concentrations results in
acidosis, a blood pH of 7.35 or less. Acidosis is seen in renal failure, a variety
of respiratory diseases in which the lungs retain carbon dioxide, and
poorly controlled diabetes mellitus.
Increased bicarbonate concentrations results in alkalosis, a blood pH
greater than 7.45 . Alkalosis is associated with hyperventilation, excess intake
or retention of bicarbonate, and loss of gastric acid due to vomiting or
potassium depletion.
helps maintain the normal blood pH of 7.4. Simply put, the blood buffer system
is activated by a buildup of positively charged hydrogen ions in the
body. When this buildup occurs, bicarbonate, a negatively charged ion,
combines with the hydrogen to produce a weak acid, or buffer, called carbonic
acid. After a series of chemical reactions, an equilibrium is established
and pH levels are held within the normal range. Variations in bicarbonate
concentrations will affect the pH levels in blood.
Bicarbonate also serves as a transport mechanism to move carbon dioxide
(CO2.) from the body tissues to the lungs where it is exhaled. Carbon
dioxide is a waste product and must be removed from the bloodstream .
Normal Range
22-26 mEq/L
Variations from Normal. Decreased bicarbonate concentrations results in
acidosis, a blood pH of 7.35 or less. Acidosis is seen in renal failure, a variety
of respiratory diseases in which the lungs retain carbon dioxide, and
poorly controlled diabetes mellitus.
Increased bicarbonate concentrations results in alkalosis, a blood pH
greater than 7.45 . Alkalosis is associated with hyperventilation, excess intake
or retention of bicarbonate, and loss of gastric acid due to vomiting or
potassium depletion.
Dec 13, 2010
Chloride (CI-) test
Chloride, an important negatively charged electrolyte,Chloride is present in the extracellular spaces in combination with sodium and hydrogen. Chloride has two main bodily functions :1-Chloride help to control the distribution of water between the cells and blood plasma, Chloride help to maintain the acid-base balance in the body.
Normal Range of Chloride
90-110 mEq/L
90-110 mEq/L
Variations from Normal. Variations in chloride levels must always be considered in relation to other electrolytes, particularly sodium and bicarbonate.
An increase in plasma chloride will correspond to an increase in sodium levels or a decrease in plasma bicarbonate levels. Measuring chlorides can be helpful in diagnosing acid-base and water balance disorders.
Increases in plasma chloride levels are seen in dehydration, eclampsia, Cushing's syndrome, and anemia. Plasma chloride is decreased with severe vomiting, diarrhea, burns, and heat exhaustion. Other diseases and syndromes that result in chloride deficits include ulcerative colitis, Addison's disease, and diabetic acidosis.
An increase in plasma chloride will correspond to an increase in sodium levels or a decrease in plasma bicarbonate levels. Measuring chlorides can be helpful in diagnosing acid-base and water balance disorders.
Increases in plasma chloride levels are seen in dehydration, eclampsia, Cushing's syndrome, and anemia. Plasma chloride is decreased with severe vomiting, diarrhea, burns, and heat exhaustion. Other diseases and syndromes that result in chloride deficits include ulcerative colitis, Addison's disease, and diabetic acidosis.
Interfering Circumstances of Chloride . Drugs that may cause an increase in chloride levels are androgens, cortisone preparations, estrogens, and nonsteroidal anti-inflammatory drugs. Decreased chloride levels can be associated with corticosteroids, hydrocortisone, and diuretics containing thiazide or mercury.
Magnesium (Mg+) test
The bulk of magnesium is combined with calcium and phosphorus in the bones, with very small amounts present in the bloodstream . Magnesium is necessary for muscular contraction, carbohydrate metabolism, and protein synthesis . It is usually filtered by the kidney through the glomerulus, and reabsorbed into the bloodstream by the renal tubule. Magnesium levels can be used as an indicator of metabolic activity and renal function. Since
magnesium is present in a variety of foods, a normal diet will maintain the body's magnesium supply.
magnesium is present in a variety of foods, a normal diet will maintain the body's magnesium supply.
Normal Range
1.6-3.0 mEq/L
1.6-3.0 mEq/L
Variations from Normal. An increase in plasma magnesium, hypermagnesemia, is usually caused by renal dysfunction or failure. Other diseases or syndromes associated with increased magnesium levels include hypothyroidism, Addison's disease, and dehydration. Excessive ingestion of magnesium via antacids, such as milk of magnesia, will also cause an increase in plasma magnesium.
Hypomagnesemia, decreased plasma magnesium, is usually due to
some type of chronic dietary or intestinal absorption problem. Diseases such as ulcerative colitis, chronic alcoholism, chronic pancreatitis, and chronic diarrhea will exhibit decreased magnesium levels. Other situations that result in hypomagnesemia include toxemia of pregnancy, hyperthyroidism, hypoparathyroidism,
cirrhosis of the liver, and excessive secretion of the hormone
aldosterone .
Magnesium deficiencies can be corrected by the proper administration of magnesium sulfate . Early symptoms of magnesium deficit include muscle cramps, tremors, and insomnia. It should be noted that decreases in urinary magnesium may be detected before decreases in plasma magnesium.
Low levels of calcium and potassium may mask the presence of hypomagnesemia.
Hypomagnesemia, decreased plasma magnesium, is usually due to
some type of chronic dietary or intestinal absorption problem. Diseases such as ulcerative colitis, chronic alcoholism, chronic pancreatitis, and chronic diarrhea will exhibit decreased magnesium levels. Other situations that result in hypomagnesemia include toxemia of pregnancy, hyperthyroidism, hypoparathyroidism,
cirrhosis of the liver, and excessive secretion of the hormone
aldosterone .
Magnesium deficiencies can be corrected by the proper administration of magnesium sulfate . Early symptoms of magnesium deficit include muscle cramps, tremors, and insomnia. It should be noted that decreases in urinary magnesium may be detected before decreases in plasma magnesium.
Low levels of calcium and potassium may mask the presence of hypomagnesemia.
Interfering Circumstances. A variety of medications can interfere with laboratory measurement of magnesium levels. Prolonged treatment involving lithium, magnesium products such as antacids and laxatives, and salicylate products such as aspirin will cause a false increase in plasma magnesium levels. This is particularly possible in the face of renal dysfunction. Administration
of calcium gluconate, which is used to replenish the body's
calcium reserves, can also interfere with testing methods and cause a false result that indicates a decreased magnesium level.
of calcium gluconate, which is used to replenish the body's
calcium reserves, can also interfere with testing methods and cause a false result that indicates a decreased magnesium level.
Calcium (Ca+) test
Approximately 98% of all calcium is stored in bones and teeth. Calcium
that is present in the bloodstream circulates in the ionized, or free state, and
in a protein-bound form with albumin. It is the ionized form of calcium that
is used in bodily processes such as muscular contraction, cardiac functioning,
hormone secretion, cell division, and the transmission of nerve impulses.
Ionized calcium is essential for blood coagulation .
Normal Range
Total plasma calcium
9.0-10.5 mg/dl
Free calcium
3.9-4.6 mg/dl
Variations from Normal. Hypercalcemia, increased plasma calcium, is associated
with many diseases but is most clinically significant in its association
with cancer. The most common cause of increased calcium in the
blood is metastatic bone disease . Cancers of the lung, breast, thyroid, kidney,
and testes are likely to metastasize to bone. Hodgkin's disease, multiple
myeloma, and leukemia may also cause hypercalcemia . Other disorders
or conditions associated with increased calcium levels are hyperparathyroidism,
Paget's disease of bone, prolonged immobilization, and Addison's
disease.
Since much of the plasma calcium is bound to albumin, decreased
plasma calcium levels, hypocalcemia, can be related to a lowered plasma albumin
level. Once this possibility has been eliminated, hypocalcemia can be
indicative of hypoparathyroidism and renal failure . Vitamin D deficiencies
and malabsorption associated with sprue, celiac disease, and pancreatic
dysfunctions contribute to decreased plasma calcium levels. Since calcium is
essential for clotting, any condition that decreases the amount of ionized calcium
can subsequently lead to coagulation and hemostasis problems.
Interfering Circumstances. Certain dietary considerations can interfere
with accurate plasma calcium test results . Vitamin D intoxication or excessive
milk ingestion, defined as three quarts of milk per day, can cause an increase
in plasma calcium.
Prescription and over-the-counter drugs such as heparin, magnesium
salts, oral contraceptives, aspirin, and corticosteroids and excessive use of
laxatives may cause a decrease in plasma calcium. Drugs that influence an
increase of plasma calcium include lithium, vitamin D, thiazide diuretics,
thyroid hormone, and hydralazine, an antihypertensive medication.
Dec 7, 2010
Potassium (K+) test
About 90% of potassium is concentrated within the cells and the remainder is contained in blood and bone. Plasma potassium influences nerve conduction, muscle activity, and, most important, cardiac function. Minimal changes in plasma potassium levels can have profound and adverse affects on heart muscle. Since the kidneys do not reabsorb or conserve potassium, adequate dietary intake is necessary to prevent potassium deficiency.
Normal Range
Adult 3.5-5.0 mEq/L
Children 3.4-4.7 mEq/L
Infant 4.1-5.3 mEq/L
Variations from Normal. An increase in plasma potassium levels, hyperkalemia, is usually attributed to renal failure . Other common causes of hyperkalemia include acidosis, Addison's disease, internal hemorrhage, and massive tissue or cellular damage. Since 90% of potassium is contained within the cells, cell damage as in cases of burns, chemotherapy, and disseminated intravascular coagulation (DIC) results in the release of potassium into the blood.
Hypokalemia, a decrease in plasma potassium, is most often associated with loss of fluid from the gastrointestinal tract.
Hypokalemia, a decrease in plasma potassium, is most often associated with loss of fluid from the gastrointestinal tract.
Therefore, any disease process that causes diarrhea or severe vomiting has the potential for creating potassium deficiency. Other disorders associated with hypokalemia include malabsorption syndromes, hyperaldosteronism (increased secretion of aldosterone), Cushing's syndrome, and renal tubular acidosis.
Hypokalemia can cause serious cardiac problems such as premature ventricular contraction, paroxysmal atrial tachycardia, ventricular tachycardia, and ventricular fibrillation. Plasma potassium levels of 2.5 mEq/L or less, or 6 .5 mEq/L or more can cause heart problems that lead to death.
Interfering Circumstances. Venipuncture, intravenous fluid administration, and certain medications can alter plasma potassium levels. The common practice of opening and closing the fist with a tourniquet in place prior to venipuncture may increase potassium levels. Intravenous fluid administration without adequate potassium supplements can lead to potassium depletion. Medications that may cause an increased potassium level include heparin, histamine, mannitol, and lithium. Drugs that may cause a decreased level are insulin, aspirin, cisplatin, and potassium wasting diuretics.
Dietary habits do not usually interfere with plasma potassium levels. A relatively well-balanced diet will provide an adequate supply of potassium. However, excessive licorice ingestion can cause a decrease in plasma potassium levels.
Dec 3, 2010
Sodium (Na+) test
Sodium has the highest extracellular concentration of all electrolytes measured in the plasma and plays a primary role in controlling the distribution of body water between extracellular and intracellular fluid.
Sodium is involved in the transmission of nerve impulses and helps heart muscle retain its ability to contract .
Because sodium is necessary for critical bodily functions, the body is able to maintain an overall base level of plasma sodium. In health the levels of sodium are kept within a very narrow range; in disease only slight changes in overall concentration are noted.
Because sodium is necessary for critical bodily functions, the body is able to maintain an overall base level of plasma sodium. In health the levels of sodium are kept within a very narrow range; in disease only slight changes in overall concentration are noted.
Normal Range
136-145 mEq/L
Variations from Normal. Hypernatremia, an increased plasma sodium level, is relatively uncommon. Hypernatremia is associated with dehydration and insufficient water intake, Conn's syndrome (the excessive secretion of aldosterone), hyperadrenalism or Cushing's disease, diabetes insipidus, and coma.
Hyponatremia, a decreased sodium level, usually reflects an excess of body water. Conditions that may cause an actual reduction in plasma sodium include severe burns, severe diarrhea, severe nephritis, diabetes, cystic fibrosis, Addison's disease (partial or complete failure of adrenocortical function), malabsorption syndrome, and certain diuretic medications.
Interfering Circumstances. Recent trauma, surgery, or shock may cause increased sodium levels . Oral contraceptives, anabolic steroids, corticosteroids, and laxatives may be linked to increased sodium levels . Decreased levels may be caused by diuretics, vasopressin, and sodium intravenous (IV) fluids .
136-145 mEq/L
Variations from Normal. Hypernatremia, an increased plasma sodium level, is relatively uncommon. Hypernatremia is associated with dehydration and insufficient water intake, Conn's syndrome (the excessive secretion of aldosterone), hyperadrenalism or Cushing's disease, diabetes insipidus, and coma.
Hyponatremia, a decreased sodium level, usually reflects an excess of body water. Conditions that may cause an actual reduction in plasma sodium include severe burns, severe diarrhea, severe nephritis, diabetes, cystic fibrosis, Addison's disease (partial or complete failure of adrenocortical function), malabsorption syndrome, and certain diuretic medications.
Interfering Circumstances. Recent trauma, surgery, or shock may cause increased sodium levels . Oral contraceptives, anabolic steroids, corticosteroids, and laxatives may be linked to increased sodium levels . Decreased levels may be caused by diuretics, vasopressin, and sodium intravenous (IV) fluids .
Dec 2, 2010
Platelet Count Tests
Platelets, also called thrombocytes, are the smallest cells in the blood. These
cells do not have a nucleus, are round or oval, flattened, disk-shaped structures,
and are necessary for coagulation . Some texts refer to platelets as fragments
of cytoplasm .
Two tests that measure or count the number of platelets are the platelet
count, which measures the number of platelets in the blood, and the mean
platelet volume (MPV), which provides information about platelet size.
cells do not have a nucleus, are round or oval, flattened, disk-shaped structures,
and are necessary for coagulation . Some texts refer to platelets as fragments
of cytoplasm .
Two tests that measure or count the number of platelets are the platelet
count, which measures the number of platelets in the blood, and the mean
platelet volume (MPV), which provides information about platelet size.
Platelet Count
A platelet count test often follows a decreased platelet count that was estimated
from a peripheral blood smear. The platelet count is an important
blood test because thrombocytopenia is the most common cause of bleeding
diseases. This count is used to evaluate bleeding disorders due to liver
disease, thrombocytopenia, and anticoagulant therapy. The test is also ordered
for patients who have diseases associated with bone marrow problems,
such as leukemia and aplastic anemia. The platelet count is expressed
as the number of platelets per cubic millimeter (mm3) of blood .
from a peripheral blood smear. The platelet count is an important
blood test because thrombocytopenia is the most common cause of bleeding
diseases. This count is used to evaluate bleeding disorders due to liver
disease, thrombocytopenia, and anticoagulant therapy. The test is also ordered
for patients who have diseases associated with bone marrow problems,
such as leukemia and aplastic anemia. The platelet count is expressed
as the number of platelets per cubic millimeter (mm3) of blood .
Normal Range
Platelets 150,000-400,000/mm3
Variations from Normal. An abnormal increase in the number of platelets is
called thrombocythemia or thrombocytosis. This increase is seen in diseases
such as malignancies, early stages of chronic granulocytic leukemia, polycythemia
vera, tuberculosis, chronic inflammatory disease, and chronic blood
loss.
A decreased platelet count is known as thrombocytopenia and can result
in significant bleeding problems. Diseases that decrease the platelet count include
pernicious and aplastic anemias, and idiopathic thrombocytopenic purpura (ITP). A low platelet count is commonly seen in AIDS cases. Exposure
to various chemicals and the toxic effects of many drugs can also lead to
thrombocytopenia . Individuals whohave serious platelet deficits often show
signs or symptoms such as petechiae, bleeding from gums, nosebleeds, and
gastrointestinal bleeding.
called thrombocythemia or thrombocytosis. This increase is seen in diseases
such as malignancies, early stages of chronic granulocytic leukemia, polycythemia
vera, tuberculosis, chronic inflammatory disease, and chronic blood
loss.
A decreased platelet count is known as thrombocytopenia and can result
in significant bleeding problems. Diseases that decrease the platelet count include
pernicious and aplastic anemias, and idiopathic thrombocytopenic purpura (ITP). A low platelet count is commonly seen in AIDS cases. Exposure
to various chemicals and the toxic effects of many drugs can also lead to
thrombocytopenia . Individuals whohave serious platelet deficits often show
signs or symptoms such as petechiae, bleeding from gums, nosebleeds, and
gastrointestinal bleeding.
Interfering Circumstances . Platelet counts can show a normal increase at
high altitudes, after strenuous exercise, and in the winter . A normal decrease
occurs on the first day of an infant's life and before menstruation.
high altitudes, after strenuous exercise, and in the winter . A normal decrease
occurs on the first day of an infant's life and before menstruation.
Mean Platelet Volume (MPV)
The mean platelet volume provides information about the relative size of
platelets, which is calculated by a cell analyzer and compared to what is observed
on a microscope slide. The diameter of the platelet is expressed in
micrometers (!gym) . The MPV is a useful diagnostic tool for thrombocytopenic
disorders.
The relative size of platelets varies with platelet production. When the
overall platelet count drops, functioning bone marrow produces younger
and larger platelets to compensate for the decreased number of platelets.
This process results in an increased mean platelet volume . Lack of bone
marrow function results in the decreased production of platelets, a diminished
platelet size, and a decreased mean platelet volume.
platelets, which is calculated by a cell analyzer and compared to what is observed
on a microscope slide. The diameter of the platelet is expressed in
micrometers (!gym) . The MPV is a useful diagnostic tool for thrombocytopenic
disorders.
The relative size of platelets varies with platelet production. When the
overall platelet count drops, functioning bone marrow produces younger
and larger platelets to compensate for the decreased number of platelets.
This process results in an increased mean platelet volume . Lack of bone
marrow function results in the decreased production of platelets, a diminished
platelet size, and a decreased mean platelet volume.
Normal Range
Platelets
2-4 gm in diameter
2-4 gm in diameter
Variations from Normal. An increase in the diameter of the platelets occurs
in systemic lupus erythematosus, idiopathic thrombocytopenic purpura in
remission, various anemias, myeloproliferative disorders, and a variety of
chronic disease processes. A decrease in the size of platelets is associated
with aplastic anemia, megaloblastic anemia, and hypersplenism.
in systemic lupus erythematosus, idiopathic thrombocytopenic purpura in
remission, various anemias, myeloproliferative disorders, and a variety of
chronic disease processes. A decrease in the size of platelets is associated
with aplastic anemia, megaloblastic anemia, and hypersplenism.
Red Blood Cell Indices
The red blood cell indices are used to determine the size of the erythrocyte
and the hemoglobin content of the red blood cells, and to identify specific
types of anemia. The indices are not individual blood cell tests, but are the result of applying mathematical formulas to the hemoglobin value, hematocrit value, and red blood cell count. Each index has its own formula that is automatically computed as a part of the complete blood count.
Red blood cell indices include the mean corpuscular volume, which
describes the average volume (size) of an individual red blood cell; the
mean corpuscular hemoglobin, the average weight of the hemoglobin in
an average red blood cell; and the mean corpuscular hemoglobin concentration,
which is the average concentration or percentage of hemoglobin
within each red blood cell.
and the hemoglobin content of the red blood cells, and to identify specific
types of anemia. The indices are not individual blood cell tests, but are the result of applying mathematical formulas to the hemoglobin value, hematocrit value, and red blood cell count. Each index has its own formula that is automatically computed as a part of the complete blood count.
Red blood cell indices include the mean corpuscular volume, which
describes the average volume (size) of an individual red blood cell; the
mean corpuscular hemoglobin, the average weight of the hemoglobin in
an average red blood cell; and the mean corpuscular hemoglobin concentration,
which is the average concentration or percentage of hemoglobin
within each red blood cell.
Mean Corpuscular Volume (MCV)
The mean corpuscular volume describes the average size of an individual
red blood cell in cubic microns (Fim3), and is calculated by multiplying the
hematocrit percentage by 10, and then dividing that result by the red blood
cell count. The size of red blood cells can have clinical significance in various
types of anemia.
red blood cell in cubic microns (Fim3), and is calculated by multiplying the
hematocrit percentage by 10, and then dividing that result by the red blood
cell count. The size of red blood cells can have clinical significance in various
types of anemia.
Normal Range
Adults and Children
80-95 gm3
Newborns
96-108 ~Lm3
80-95 gm3
Newborns
96-108 ~Lm3
Variations from Normal. When there is a decrease in the mean corpuscular
volume, the erythrocytes are microcytic, or smaller than normal. Microcytic
red blood cells are seen in iron deficiency anemia, lead poisoning,
and thalassemia .
An increase in the mean corpuscular volume indicates that the red
blood cells are macrocytic, or larger than normal. Pernicious anemia is associated
with macrocytic red blood cells.
When the mean corpuscular volume is within normal range, the red
blood cells are normocytic, or of normal size. Aplastic, hemolytic, and temporary
blood loss anemia are associated with red blood cells that are normal
in size.
volume, the erythrocytes are microcytic, or smaller than normal. Microcytic
red blood cells are seen in iron deficiency anemia, lead poisoning,
and thalassemia .
An increase in the mean corpuscular volume indicates that the red
blood cells are macrocytic, or larger than normal. Pernicious anemia is associated
with macrocytic red blood cells.
When the mean corpuscular volume is within normal range, the red
blood cells are normocytic, or of normal size. Aplastic, hemolytic, and temporary
blood loss anemia are associated with red blood cells that are normal
in size.
Mean Corpuscular Hemoglobin (MCH)
The mean corpuscular hemoglobin is the average weight of hemoglobin
in an average red blood cell. This weight is calculated by multiplying the hemoglobin count by 10 and then dividing by the red blood cell count.
The result is reported in picograms (pg). The mean corpuscular hemoglobin
is adequate for diagnosing severely anemic patients, but is a nonspecific
result.
in an average red blood cell. This weight is calculated by multiplying the hemoglobin count by 10 and then dividing by the red blood cell count.
The result is reported in picograms (pg). The mean corpuscular hemoglobin
is adequate for diagnosing severely anemic patients, but is a nonspecific
result.
Normal Range
Adults and Children
27-31 pg
Newborns
32-38 pg
Adults and Children
27-31 pg
Newborns
32-38 pg
Variations from Normal. An increase in the mean corpuscular hemoglobin
is seen in macrocytic anemia, while a decrease is associated with microcytic
anemia .
is seen in macrocytic anemia, while a decrease is associated with microcytic
anemia .
Mean Corpuscular Hemoglobin Concentration (MCHC)
The mean corpuscular hemoglobin concentration measures the average
concentration or percentage of hemoglobin within each red blood cell. The
MCHC is calculated by dividing the hemoglobin value by the hematocrit
value, and multiplying the result by 100. The mean corpuscular hemoglobin
concentration is most valuable for classifying anemias.
concentration or percentage of hemoglobin within each red blood cell. The
MCHC is calculated by dividing the hemoglobin value by the hematocrit
value, and multiplying the result by 100. The mean corpuscular hemoglobin
concentration is most valuable for classifying anemias.
Normal Range
Adults and Children 32-36%
Newborns 32-33%
Adults and Children 32-36%
Newborns 32-33%
Variations from Normal. A decrease in the mean corpuscular hemoglobin
concentration indicates that the red blood cells contain less hemoglobin
than normal and is classified as hypochromic anemia, which means the red
blood cells lack color. Iron deficiency anemia is the most common type of
hypochromic anemia .
An increase in the mean corpuscular hemoglobin concentration usually
indicates spherocytosis . Spherocytosis is defined as an increase in the
number of abnormal, spheric, red blood cells called spherocytes. Sphero
cytes have a smaller amount of membrane and a full complement of hemoglobin
so the mean corpuscular hemoglobin concentration is elevated.
Table 1-2 lists the classifications of anemia based on the red blood cell indices
values.
concentration indicates that the red blood cells contain less hemoglobin
than normal and is classified as hypochromic anemia, which means the red
blood cells lack color. Iron deficiency anemia is the most common type of
hypochromic anemia .
An increase in the mean corpuscular hemoglobin concentration usually
indicates spherocytosis . Spherocytosis is defined as an increase in the
number of abnormal, spheric, red blood cells called spherocytes. Sphero
cytes have a smaller amount of membrane and a full complement of hemoglobin
so the mean corpuscular hemoglobin concentration is elevated.
Table 1-2 lists the classifications of anemia based on the red blood cell indices
values.
Erythrocyte Sedimentation Rate (ESR, Sed Rate)
The erythrocyte sedimentation rate is the rate at which red blood cells settle
out of unclotted blood in an hour. The results are expressed as millimeters
per hour (mm/hr). This is a nonspecific test because it does not identify any
particular disease. In fact, the ESR can be normal in many disease processes.
The erythrocyte sedimentation rate is useful in determining the
progress of inflammatory diseases, rheumatoid arthritis, rheumatic fever,
and acute myocardial infarction. The speed at which the red blood cells fall
to the bottom of the test tube corresponds to the degree of inflammation.
out of unclotted blood in an hour. The results are expressed as millimeters
per hour (mm/hr). This is a nonspecific test because it does not identify any
particular disease. In fact, the ESR can be normal in many disease processes.
The erythrocyte sedimentation rate is useful in determining the
progress of inflammatory diseases, rheumatoid arthritis, rheumatic fever,
and acute myocardial infarction. The speed at which the red blood cells fall
to the bottom of the test tube corresponds to the degree of inflammation.
Normal Range
Men <50 yrs 0-10 mm/hr
>50 yrs 0-13 mm/hr
Women <50 yrs 0-13 mm/hr
>50 yrs 0-20 mm/hr
Children 0-10 mm/hr
>50 yrs 0-13 mm/hr
Women <50 yrs 0-13 mm/hr
>50 yrs 0-20 mm/hr
Children 0-10 mm/hr
Variations from Normal. An increase in the sed rate is usually due to inflammation
or tissue injury. When sed rates are greater than 100 mm/hr,
likely causes, except in pregnancy, are infections, malignancies or collagen
vascular diseases. A decrease in the sed rate is associated with polycythemia
vera, sickle cell anemia, and a deficiency in the plasma protein fibrinogen.
or tissue injury. When sed rates are greater than 100 mm/hr,
likely causes, except in pregnancy, are infections, malignancies or collagen
vascular diseases. A decrease in the sed rate is associated with polycythemia
vera, sickle cell anemia, and a deficiency in the plasma protein fibrinogen.
Interfering Circumstances. Many factors can influence the erythrocyte sedimentation
rate. Refrigerated blood samples, blood left standing for more than two hours before the test, menstruation, and pregnancy will cause a
nonpathological increase in this test. Age and certain drug therapies may
also cause variations in test results .
Red Blood Cell Tests
One of the major functions of erythrocytes is to carry oxygen to all parts of the body. In order to do this efficiently, there must be an adequate number of red blood cells and the red blood cells must contain an adequate supply of functioning hemoglobin. Erythrocyte tests include the red blood cell count, hematocrit, and hemoglobin. These tests are closely related and provide different ways to measure the adequacy of red blood cell production and function. Other common red blood cell tests include red blood cell indices
and the erythrocyte sedimentation rate.
and the erythrocyte sedimentation rate.
Red Blood Cell Count; Erythrocyte Count (RBC)
The red blood cell count identifies the number of red blood cells found in a cubic millimeter of blood (mm3) . The count is usually accomplished by an electronic or automated counting device.
Normal Range
Men
4.7-6.1 million/mm3
Women
4.2-5.4 million/mm3
Infants and Children
3 .8-5.5 million/mm.3
Newborns
4.8-7.1 million/mm3
Men
4.7-6.1 million/mm3
Women
4.2-5.4 million/mm3
Infants and Children
3 .8-5.5 million/mm.3
Newborns
4.8-7.1 million/mm3
Variations from Normal. A decrease in the number or function of red blood cells is called anemia. Factors that can cause anemia are decreased red blood cell production, increased red blood cell destruction, and blood loss.
Certain diseases can also cause a decrease in red blood cells. Some of these diseases include Hodgkin's disease, leukemia, rheumatic fever, and diseases that affect the bone marrow where red blood cells are produced.
An increase in the number of red blood cells is called erythrocytosis, a slight increase, or erythremia, an excessive increase. Many factors can contribute to this increase, such as an overproduction of red blood cells or a decrease in the amount of blood plasma. Conditions such as dehydration,
severe diarrhea, acute poisoning, and chronic lung disease can also cause an increase in the red blood cell count.
Certain diseases can also cause a decrease in red blood cells. Some of these diseases include Hodgkin's disease, leukemia, rheumatic fever, and diseases that affect the bone marrow where red blood cells are produced.
An increase in the number of red blood cells is called erythrocytosis, a slight increase, or erythremia, an excessive increase. Many factors can contribute to this increase, such as an overproduction of red blood cells or a decrease in the amount of blood plasma. Conditions such as dehydration,
severe diarrhea, acute poisoning, and chronic lung disease can also cause an increase in the red blood cell count.
Variations from Normal. A decrease in the number or function of red blood cells is called anemia. Factors that can cause anemia are decreased red blood cell production, increased red blood cell destruction, and blood loss.
Certain diseases can also cause a decrease in red blood cells. Some of these diseases include Hodgkin's disease, leukemia, rheumatic fever, and diseases that affect the bone marrow where red blood cells are produced.
An increase in the number of red blood cells is called erythrocytosis, a slight increase, or erythremia, an excessive increase. Many factors can contribute to this increase, such as an overproduction of red blood cells or a de crease in the amount of blood plasma. Conditions such as dehydration,
severe diarrhea, acute poisoning, and chronic lung disease can also cause an increase in the red blood cell count.
Certain diseases can also cause a decrease in red blood cells. Some of these diseases include Hodgkin's disease, leukemia, rheumatic fever, and diseases that affect the bone marrow where red blood cells are produced.
An increase in the number of red blood cells is called erythrocytosis, a slight increase, or erythremia, an excessive increase. Many factors can contribute to this increase, such as an overproduction of red blood cells or a de crease in the amount of blood plasma. Conditions such as dehydration,
severe diarrhea, acute poisoning, and chronic lung disease can also cause an increase in the red blood cell count.
Interfering Circumstances. The results of the red blood cell count can be altered by several nondisease situations. These would include the posture or position of the patient when the blood was drawn, exercise, age, altitude, pregnancy, and various legal and illegal drugs.
Hematocrit (Hct); Packed Cell Volume (PCV)
The purpose of the hematocrit or packed cell volume (PCV) test is to determine the percentage of red blood cells in whole blood. The hematocrit is reported as a percentage because it is the proportion of red blood cells compared
to the amount of plasma in whole blood.
The term "hematocrit" literally means to separate blood. A sample of blood is placed in a tube that contains an anticoagulant, which prevents clotting. The sample is mixed, and three distinct layers will separate out.
Figure 1-3 shows these three layers.
The bottom layer represents the hematocrit value and is composed of red blood cells, approximately 45% of the total blood volume, with variations allowed for men and women. The middle layer is a thin, whitish layer called the buffy coat, approximately 1% of the blood volume, which is made up of white blood cells and platelets . The upper layer is the liquid plasma, which comprises the remainder of the total blood volume.
Variations from Normal. Since the hematocrit is the percentage of red blood cells in whole blood, a decrease in hematocrit values is an indication of some type of anemia. Therefore, anything that causes a decrease in the number of red blood cells will result in a decrease in the hematocrit. Blood loss, conditions where there is increased destruction of red blood cells, leukemia, and diseases that interfere with red blood cell production will exhibit a low hematocrit. It must also be noted that overhydration, or an increase in plasma volume for any reason, can result in a relative decreased
hematocrit value.
An apparent increase in the hematocrit must be closely analyzed . Since the hematocrit is reported as a percentage of red blood cells to blood volume, any decrease in the volume of plasma would result in a mathematical increase in the hematocrit. Therefore, if the patient has lost blood plasma, the blood will be very concentrated and the hematocrit will be increased.
When an increase in hematocrit is related to the increase in the actual number of red blood cells, erythrocytosis or polycythemia is the result.
Interfering Circumstances. Factors that can influence hematocrit results include age, pregnancy, gender, and living in high altitudes.
Hemoglobin (Hgb) Hemoglobin is a protein-iron complex that is the main constituent of red blood cells. In fact, red blood cells contain approximately 90% hemoglobin.
The primary functions of hemoglobin are to transport oxygen from the lungs to the cells and to carry carbon dioxide from the cells to the lungs to be expelled. The hemoglobin test is used to indirectly evaluate the oxygen carrying capacity of the red blood cells. The hemoglobin count is also used
to diagnose, evaluate, or assess the treatment of various types of anemia.
Normal Range
Men 42-52%
Women 37-47% (in pregnancy: >33%)
Children 30-42%
Newborns 44-64%
to the amount of plasma in whole blood.
The term "hematocrit" literally means to separate blood. A sample of blood is placed in a tube that contains an anticoagulant, which prevents clotting. The sample is mixed, and three distinct layers will separate out.
Figure 1-3 shows these three layers.
The bottom layer represents the hematocrit value and is composed of red blood cells, approximately 45% of the total blood volume, with variations allowed for men and women. The middle layer is a thin, whitish layer called the buffy coat, approximately 1% of the blood volume, which is made up of white blood cells and platelets . The upper layer is the liquid plasma, which comprises the remainder of the total blood volume.
Variations from Normal. Since the hematocrit is the percentage of red blood cells in whole blood, a decrease in hematocrit values is an indication of some type of anemia. Therefore, anything that causes a decrease in the number of red blood cells will result in a decrease in the hematocrit. Blood loss, conditions where there is increased destruction of red blood cells, leukemia, and diseases that interfere with red blood cell production will exhibit a low hematocrit. It must also be noted that overhydration, or an increase in plasma volume for any reason, can result in a relative decreased
hematocrit value.
An apparent increase in the hematocrit must be closely analyzed . Since the hematocrit is reported as a percentage of red blood cells to blood volume, any decrease in the volume of plasma would result in a mathematical increase in the hematocrit. Therefore, if the patient has lost blood plasma, the blood will be very concentrated and the hematocrit will be increased.
When an increase in hematocrit is related to the increase in the actual number of red blood cells, erythrocytosis or polycythemia is the result.
Interfering Circumstances. Factors that can influence hematocrit results include age, pregnancy, gender, and living in high altitudes.
Hemoglobin (Hgb) Hemoglobin is a protein-iron complex that is the main constituent of red blood cells. In fact, red blood cells contain approximately 90% hemoglobin.
The primary functions of hemoglobin are to transport oxygen from the lungs to the cells and to carry carbon dioxide from the cells to the lungs to be expelled. The hemoglobin test is used to indirectly evaluate the oxygen carrying capacity of the red blood cells. The hemoglobin count is also used
to diagnose, evaluate, or assess the treatment of various types of anemia.
Normal Range
Men 42-52%
Women 37-47% (in pregnancy: >33%)
Children 30-42%
Newborns 44-64%
A normal red blood cell count does not automatically translate into a normal hemoglobin value. Abnormal production of any portion of hemoglobin could result in decreased levels of hemoglobin per red blood cells.
Once a sample of blood is taken, the hemoglobin level is determined by automated electronic equipment. Generally, the hemoglobin value is approximately one-third of the hematocrit value. Therefore, a person with a 45% hematocrit would be expected to have approximately 15 grams of hemoglobin per deciliter of blood (15 g/dl).
Once a sample of blood is taken, the hemoglobin level is determined by automated electronic equipment. Generally, the hemoglobin value is approximately one-third of the hematocrit value. Therefore, a person with a 45% hematocrit would be expected to have approximately 15 grams of hemoglobin per deciliter of blood (15 g/dl).
Normal Range
Men
14-18 g/dl
Women
12-16 g/dl (in pregnancy: >11 g/dl)
Children
11-16 g/dl
Newborns
14-24 g/dl
Men
14-18 g/dl
Women
12-16 g/dl (in pregnancy: >11 g/dl)
Children
11-16 g/dl
Newborns
14-24 g/dl
Variations from Normal. Hemoglobin levels can exhibit temporary variations immediately after blood transfusions, hemorrhages, and burns. A decrease in the hemoglobin level can be found in various anemias. Other diseases and factors that result in a hemoglobin decrease include hyperthyroidism, cirrhosis of the liver, transfusions of incompatible blood, Hodgkin's disease, lymphoma, and reactions to various chemicals and drugs. Since iron
is necessary for the production of hemoglobin, a decreased hemoglobin level may signal the need for blood iron tests. Blood Chemistry Tests.
An increase in hemoglobin levels is found in any situation that results in an increased number of healthy red blood cells. Diseases associated with increased hemoglobin values are chronic obstructive pulmonary disease
and congestive heart failure .
Interfering Circumstances. Factors that can affect hemoglobin results include pregnancy, altitude, age, gender, and excessive fluid intake. Various medications may cause an increase or decrease in hemoglobin levels.
is necessary for the production of hemoglobin, a decreased hemoglobin level may signal the need for blood iron tests. Blood Chemistry Tests.
An increase in hemoglobin levels is found in any situation that results in an increased number of healthy red blood cells. Diseases associated with increased hemoglobin values are chronic obstructive pulmonary disease
and congestive heart failure .
Interfering Circumstances. Factors that can affect hemoglobin results include pregnancy, altitude, age, gender, and excessive fluid intake. Various medications may cause an increase or decrease in hemoglobin levels.
Complete Blood Count (CBC)
The complete blood count (CBC) is a laboratory test that identifies the
number of red and white blood cells per cubic millimeter (mm3) of blood.
It is one of the most routinely performed blood tests and provides valuable
information about the patient's state of health. The CBC measures and evaluates
the cellular component of blood.
The tests included in the complete blood count are white blood cell
tests, which include the white blood cell count and the differential white
cell count; red blood cell tests, which include the red blood cell count,
hematocrit, and hemoglobin count; red blood cell indices, which include
the mean corpuscular volume, the mean corpuscular hemoglobin, and the
mean corpuscular hemoglobin concentration; and the thrombocyte test, or
platelet count.
number of red and white blood cells per cubic millimeter (mm3) of blood.
It is one of the most routinely performed blood tests and provides valuable
information about the patient's state of health. The CBC measures and evaluates
the cellular component of blood.
The tests included in the complete blood count are white blood cell
tests, which include the white blood cell count and the differential white
cell count; red blood cell tests, which include the red blood cell count,
hematocrit, and hemoglobin count; red blood cell indices, which include
the mean corpuscular volume, the mean corpuscular hemoglobin, and the
mean corpuscular hemoglobin concentration; and the thrombocyte test, or
platelet count.
HEMATOLOGY NORMAL RANGE
Hemoglobin 12-16 g/dl
Hematocrit 37-47%
Erythrocytes 4.2-5.4
Leukocytes 5000-10000/mm3
Neutrophils 55-70%
Monocytes 2-8%
Lymphocytes 20-40%
Basophils 0.5-1%
Eosinophils 1-4%
Platelet Count 140,000-400,000
MPV 2-4 m/diameter
White Blood Cell Tests
The white blood cell count and the differential white blood cell count
identify the number and type of white blood cells present in the blood.
Both tests provide useful diagnostic information .
White Blood Cell Count; Leukocyte Count (WBC)
The white blood cell count identifies the number of white blood cells in a
specified volume of blood. The white cell count is then expressed as so
many thousand white blood cells per cubic millimeter (/mm3). Cell counting
is usually accomplished by an automated cell counter, but can be done
using a microscope with a special counting chamber.
Normal Range
Adults and Children 5000-10,000/mm 3
Children 2 years or younger 6200-17,000/mm 3
Newborns 9000-30,000/mm3
Variations from Normal. An increase in the overall number of white blood
cells is called leukocytosis . This is a very general term and can be the result
of a wide variety of conditions such as infection, hemorrhage, trauma, malignancy,
general hematologic problems, and leukemia. Adecrease in the
number of white blood cells is called leukopenia, andcan occur for reasons
that include viral infections, bone marrow disorders, spleen disorders, immune
problems, AIDS, and nutritional deficiencies .
Interfering Circumstances. The white cell count is affected by the time of
day (lower levels in the morning and a late afternoon peak), age, and gender.
Smoking can cause up to a 30% increase in total white blood cells.
Differential White Blood Cell Count; Differential Leukocyte Count (diff)
The differential white blood cell count is used to identify the percentage of
each type of white cell relative to the total number of leukocytes . The five
types of leukocytes are neutrophils, eosinophils, basophils, monocytes, and
lymphocytes. Each leukocyte has a unique function . Table 1-1 identifies
each type of white cell and its function.
Since each of the white cells is unique, normal range and clinical implications
of the increase or decrease in each type are presented individually .
Neutrophils
Neutrophils are the most numerous of the white cells and appear to be the
body's first defense against bacterial infection and severe stress . During an acute bacterial infection, neutrophils function as phagocytes. Neutrophils
remain in the blood stream for approximately 7-10 hours.
Neutrophils are also known as segmented neutrophils (segs) or polymorphonuclear
leukocytes (PMNs, polys). The names given to the neutrophils
depend on the maturity of the cells and the appearance of the
nucleus of the cells. Mature neutrophils are identified by their characteristic
segmented or lobed nucleus and are called segs, or segmented neutrophils.
Immature neutrophils are called bands or stabs because the nucleus
is not segmented.
Normal Range (Adult)
Neutrophils 55-70% of all white cells
Variations from Normal. An increase in the number of circulating neutrophils
is called neutrophilia and can be caused by various bacterial infections; inflammatory
diseases such as rheumatic fever, rheumatoid arthritis, stress, tissue
death or damage; and granulocytic leukemia. When reporting an increase
in neutrophils, the terms "shift to the left" or "shift to the right" may be used.
A shift to the left simply means that the increase in neutrophils is due to an increase
in the number of immature neutrophils. A shift to the right, although
rarely used, may indicate that abnormal or mature neutrophils predominate.
Adecrease in the number of circulating neutrophils is called neutropenia,
and can be caused by viral diseases and infections such as measles,
mumps, rubella, hepatitis, and influenza. Bone marrow injury and anorexia
nervosa can exhibit neutropenia.
Interfering Circumstances. Various treatments, such as radiation therapy and
chemotherapy, carry the risk of decreasing neutrophils. Antibiotics, psychotropic
medications, and some antidepressants can also play a role in neutropenia.
Lymphocytes (Lymphs)
Lymphocytes (lymphs) are an important part of the immune system and
play an active role in combating acute viral and chronic bacterial infections.
There are two types of lymphocytes, T cells and B cells. The differential
count does not identify or enumerate the number of T and B cells.
Normal Range (Adult)
Lymphocytes
20-40% of all white cells
Variations from Normal. An increase in the number of lymphocytes is called
lymphocytosis and is seen in a variety of diseases. Viral diseases such as
rubella, measles, mumps, viral respiratory infections, atypical pneumonia,
infectious hepatitis, and infectious mononucleosis exhibit lymphocytosis .
Bacterial infections such as syphilis and pertussis can also cause lymphocytosis.
Malignant causes of lymphocytosis are lymphocytic leukemia and lymphoma.
A decrease in lymphocytes is called lymphocytopenia and is seen primarily
when the immune system is suppressed as in diseases such as AIDS
and systemic lupus erythematosus.
Monocytes (Monos)
Monocytes (monos), although small in number, perform an important defense
function in the body. These large cells are phagocytes and respond to
bacteria in the same manner as neutrophils. Monocytes remain in circulation
longer than neutrophils and phagocytize bacterial and cellular debris.
Phagocytosis is the process of engulfing and destroying microorganisms
and cellular debris. Monocytes also act as phagocytes in some chronic inflammatory
diseases such as arthritis.
Normal Range
Monocytes
2-8% of all white cells
Variations from Normal. An increase in the number of monocytes is called
monocytosis and is seen during infections such as tuberculosis and bacterial
endocarditis. Diseases such as chronic ulcerative colitis, malaria,
rheumatoid arthritis, and hemolytic anemia can exhibit an increase in the
monocyte count. A decreased monocyte count is not usually identified
with any specific disease processes.
Eosinophils and Basophils (Eosinos, Basos)
Eosinophils (eosinos) are minimally phagocytic, but play a role in the antigen-
antibody response, in allergic reactions, in combating parasitic infections,
and in the dissolution of blood clots. The main function of eosinophils
seems to be to prevent the excessive spread of inflammation. Basophils
(basos) play an important role in allergic reactions by releasing the histamine
that is responsible for allergy symptoms.
Normal Range
Eosinophils 1-4% of all white cells
Basophils 0.5-1% of all white cells
Variations from Normal. An increase in eosinophils is called eosinophilia
and is associated with allergy attacks, asthma, hay fever, and parasitic infections.
Certain skin diseases, tuberculosis, Hodgkin's disease, and granulocytic
leukemia result in an increase in eosinophils. Adecrease in eosinophils
is called eosinopenia and is associated with an increase in adrenal steroid
production and acute bacterial or viral inflammation .
An increase in basophils is called basophilia, and is seen in myeloproliferative
diseases such as polycythemia vera and chronic granulocytic
leukemia. Chicken pox, small pox, chronic sinusitis, and ulcerative colitis
may also be present with basophilia. Because the normal basophil count is
small to begin with, a decrease in number may not be detected . However,
prolonged steroid therapy, hormone imbalance, thyrotoxicosis, and severe
allergic reactions often result in a basophil decrease.
Interfering Circumstances. As with other white blood cell counts, age, stress,
time of day, and steroid therapy can interfere with eosinophil and basophil
counts.
Dec 1, 2010
Variations in Blood Cell Structure and Function
Variations in the structure and function of blood cells may not only cause
disease, but may also occur as a result of a disease process . In health, mature,
functioning blood cells enter the bloodstream and are able to carry out
the work of the blood. In disease, immature, poorly formed cells may be
found in the blood and are often unable to carry out the work of the blood.
Blood Cell Tests
The blood cell tests presented in this chapter focus on cell number, size, or
structure . Tests are presented by individual cell type and include diagnoses
related to variations from normal.
Normal ranges of blood cell tests depend on a variety of factors including
the age of the individual being tested and the individual laboratory standards
where the tests are run. There are a variety of factors that may cause an
abnormal test result. These factors are listed with the description of each test.
disease, but may also occur as a result of a disease process . In health, mature,
functioning blood cells enter the bloodstream and are able to carry out
the work of the blood. In disease, immature, poorly formed cells may be
found in the blood and are often unable to carry out the work of the blood.
Blood Cell Tests
The blood cell tests presented in this chapter focus on cell number, size, or
structure . Tests are presented by individual cell type and include diagnoses
related to variations from normal.
Normal ranges of blood cell tests depend on a variety of factors including
the age of the individual being tested and the individual laboratory standards
where the tests are run. There are a variety of factors that may cause an
abnormal test result. These factors are listed with the description of each test.
Variations in the Number ofBlood Cells
The blood cell tests deal primarily with variations in the
number of each type of blood cell. The results of these tests may not identify
a specific disease, but they do provide valuable information about the patient's
condition.
There are several general terms associated with the increase or decrease
in the number of each type of blood cell. An overview of these terms is presented
here. The diagnostic significance of this information is detailed in
the discussion of each individual blood cell test.
number of each type of blood cell. The results of these tests may not identify
a specific disease, but they do provide valuable information about the patient's
condition.
There are several general terms associated with the increase or decrease
in the number of each type of blood cell. An overview of these terms is presented
here. The diagnostic significance of this information is detailed in
the discussion of each individual blood cell test.
Variations in the Number of Erythrocytes
Red blood cell disorders are classified as anemia, erythrocytosis, and erythremia.
Anemia is defined as a reduction in the number of circulating red
blood cells due to blood loss; a decreased production of red cells; an increased
destruction of red blood cells; or a deficiency of hemoglobin. Erythrocytosis
is defined as a slight increase in circulating red blood cells,
while erythremia is an excessive increase in circulating red blood cells.
Variations in the number of circulating red blood cells can be caused by
a variety of conditions. However, if the clinician suspects that there is a
problem with the production of red blood cells, a bone marrow aspiration
may be ordered. Bone marrow can be withdrawn from the posterior iliac
crest, anterior iliac crest, and the sternum. Bone marrow aspiration is performed
by a physician and requires written consent from the patient or the
patient's legal representative.
Anemia is defined as a reduction in the number of circulating red
blood cells due to blood loss; a decreased production of red cells; an increased
destruction of red blood cells; or a deficiency of hemoglobin. Erythrocytosis
is defined as a slight increase in circulating red blood cells,
while erythremia is an excessive increase in circulating red blood cells.
Variations in the number of circulating red blood cells can be caused by
a variety of conditions. However, if the clinician suspects that there is a
problem with the production of red blood cells, a bone marrow aspiration
may be ordered. Bone marrow can be withdrawn from the posterior iliac
crest, anterior iliac crest, and the sternum. Bone marrow aspiration is performed
by a physician and requires written consent from the patient or the
patient's legal representative.
Variations in the Number of Leukocytes
White blood cell disorders fall into one of two categories: leukocytosis, a
slight increase in the number of white cells, or leukopenia (leukocytopenia),
a decrease in the number of white cells. Since there are many types of
white blood cells, the cell count of each specific type can indicate a variety
of problems or diagnoses . Specific cell counts and their diagnostic significance
are presented with each blood cell test.
White blood cell disorders fall into one of two categories: leukocytosis, a
slight increase in the number of white cells, or leukopenia (leukocytopenia),
a decrease in the number of white cells. Since there are many types of
white blood cells, the cell count of each specific type can indicate a variety
of problems or diagnoses . Specific cell counts and their diagnostic significance
are presented with each blood cell test.
Variations in the Number of Thrombocytes
Thrombocyte or platelet disorders are classified as thrombocytopenia, a decrease
in the number of platelets, or thrombocytosis, a slight increase in the
number of platelets . An excessive increase in the number of platelets is often
referred to as thrombocythemia. Variations in the number of thrombocytes
can be the result of bone marrow disorders. Thrombocytopenia is the most
common cause of bleeding disorders. Thrombocytosis can be the result of a
variety of conditions such as acute blood loss, following splenectomy, some
anemias, and chronic diseases. Other causes of thrombocytosis are related to
specific hematological disorders, such as autoimmune hemolytic anemia.
in the number of platelets, or thrombocytosis, a slight increase in the
number of platelets . An excessive increase in the number of platelets is often
referred to as thrombocythemia. Variations in the number of thrombocytes
can be the result of bone marrow disorders. Thrombocytopenia is the most
common cause of bleeding disorders. Thrombocytosis can be the result of a
variety of conditions such as acute blood loss, following splenectomy, some
anemias, and chronic diseases. Other causes of thrombocytosis are related to
specific hematological disorders, such as autoimmune hemolytic anemia.
Blood Collection Procedures
There are two basic types of blood collection procedures: skin (dermal)
puncture and venipuncture. Skin puncture is used to collect capillary blood.
The puncture site for adults and children is usually the fingertip, and for infants
the sites are the heel or the great toe. Venipuncture is necessary for
most diagnostic tests. As the name implies, blood is withdrawn from a vein
through the use of a needle and special collection tube or syringe.
puncture and venipuncture. Skin puncture is used to collect capillary blood.
The puncture site for adults and children is usually the fingertip, and for infants
the sites are the heel or the great toe. Venipuncture is necessary for
most diagnostic tests. As the name implies, blood is withdrawn from a vein
through the use of a needle and special collection tube or syringe.
Composition of Blood
The average adult has about 5 liters (5-6 quarts) of blood, which is divided
into plasma and cells. Plasma, which accounts for about 3 liters, is the liquid
portion of blood. The cells, which account for about 2 liters, are referred
to as the formed elements or cellular component of blood.
Blood Cells
into plasma and cells. Plasma, which accounts for about 3 liters, is the liquid
portion of blood. The cells, which account for about 2 liters, are referred
to as the formed elements or cellular component of blood.
Blood Cells
Blood cells are classified as erythrocytes (red blood cells), leukocytes (white
blood cells), and thrombocytes, also called platelets. Each type of blood cell
has specific functions. A brief description of the cell, its functions, and
unique characteristics follows.
blood cells), and thrombocytes, also called platelets. Each type of blood cell
has specific functions. A brief description of the cell, its functions, and
unique characteristics follows.
Erythrocytes:
Erythrocytes are the most numerous cells, second in size, and
easily identified by their unique biconcave disk shape. Red blood cells are
formed in the red bone marrow, live about 120 days, and are removed from
the blood stream by phagocytes, cells that are able to engulf and digest cellular
debris. The spleen is the primary site of phagocytosis of aged red
blood cells. The liver and bone marrow also play a role in removing or recycling
red blood cells.
The main functions of erythrocytes are to carry oxygen to all parts of
the body and to bring carbon dioxide to the lungs. The hemoglobin in the
red blood cell is the carrier for oxygen and carbon dioxide . Therefore, in
order for oxygen and carbon dioxide to move throughout the body, an adequate
number of mature, functioning red blood cells must be available .
The red blood cells must also contain the appropriate amount of hemoglobin.
easily identified by their unique biconcave disk shape. Red blood cells are
formed in the red bone marrow, live about 120 days, and are removed from
the blood stream by phagocytes, cells that are able to engulf and digest cellular
debris. The spleen is the primary site of phagocytosis of aged red
blood cells. The liver and bone marrow also play a role in removing or recycling
red blood cells.
The main functions of erythrocytes are to carry oxygen to all parts of
the body and to bring carbon dioxide to the lungs. The hemoglobin in the
red blood cell is the carrier for oxygen and carbon dioxide . Therefore, in
order for oxygen and carbon dioxide to move throughout the body, an adequate
number of mature, functioning red blood cells must be available .
The red blood cells must also contain the appropriate amount of hemoglobin.
Leukocytes:
Leukocytes are the largest in size and represent the fewest number
of blood cells. There are two major types of leukocytes: granulocytes and
agranulocytes. Granulocytes, also called polymorphonuclear leukocytes
(PMNs), are the most numerous and have dark-staining granules in the cytoplasm.
These cells are further classified as neutrophils, eosinophils, and basophils.
Agranulocytes, also called mononuclear leukocytes, do not have
dark-staining granules in the cytoplasm. Agranulocytes are further classified
as lymphocytes or monocytes.
Leukocytes are chiefly responsible for fighting infection by identifying,
engulfing, and destroying foreign organisms . They are active in the immune
response by producing antibodies to foreign organisms. Additional infor
mation about the function of each type of leukocyte is discussed with the
blood cell tests related to the specific type of leukocyte.
of blood cells. There are two major types of leukocytes: granulocytes and
agranulocytes. Granulocytes, also called polymorphonuclear leukocytes
(PMNs), are the most numerous and have dark-staining granules in the cytoplasm.
These cells are further classified as neutrophils, eosinophils, and basophils.
Agranulocytes, also called mononuclear leukocytes, do not have
dark-staining granules in the cytoplasm. Agranulocytes are further classified
as lymphocytes or monocytes.
Leukocytes are chiefly responsible for fighting infection by identifying,
engulfing, and destroying foreign organisms . They are active in the immune
response by producing antibodies to foreign organisms. Additional infor
mation about the function of each type of leukocyte is discussed with the
blood cell tests related to the specific type of leukocyte.
Thrombocytes:
Thrombocytes, also called platelets, are essential for coagulation.
Without an adequate number of functioning platelets, an individual
would bleed to death.
Without an adequate number of functioning platelets, an individual
would bleed to death.
Plasma
Plasma, the fluid or liquid component of blood, is about 90% water. The
remaining constituents of plasma include a variety of substances either
dissolved or suspended in this watery medium: proteins; minerals such
as calcium, potassium, and sodium; glucose; lipids; cholesterol; and
waste products. Other components include antibodies, enzymes, and hormones.
The primary functions of plasma are to transport nutrients and other
necessary chemicals to all body cells and to bring waste products to the
body systems and organs that serve as waste disposal centers.
remaining constituents of plasma include a variety of substances either
dissolved or suspended in this watery medium: proteins; minerals such
as calcium, potassium, and sodium; glucose; lipids; cholesterol; and
waste products. Other components include antibodies, enzymes, and hormones.
The primary functions of plasma are to transport nutrients and other
necessary chemicals to all body cells and to bring waste products to the
body systems and organs that serve as waste disposal centers.
Nov 22, 2010
Uric Acid analysis
the gout disease symptoms:
pain in the feet (usually at the corm of the foot) increases after wake up .
pain in the large finger of the foot.
Note:
if the patient have this symptoms and the UA analysis result is normal he must take the drug of gout disease.
Procedure:
1. Put 1 ml of the uric acid reagent in each of two small test tubes.
2. Withdraw 20µ of serum by micropipette and put them in one of the two tubes and sign it as test tube .
3. Withdraw 20µ of uric acid standard and put them in the other tube and sign it as standard tube .
4. Leave the two tubes in water bath for 5 minutes or in room temperature for 10 minutes .
5. Use the wave length 546 nm for measuring.
6. Put the standard and record the reading then put the tested serum and record the reading.
Calculation:
[The reading of test / The reading of standard ] * conc. of UA standard (usually 6 or 5 mg/dl) .
Normal values:
♂ : 3.4 – 7.0 mg/dl
♀ : 2.4 – 5.7 mg/dl
pain in the feet (usually at the corm of the foot) increases after wake up .
pain in the large finger of the foot.
Note:
if the patient have this symptoms and the UA analysis result is normal he must take the drug of gout disease.
Procedure:
1. Put 1 ml of the uric acid reagent in each of two small test tubes.
2. Withdraw 20µ of serum by micropipette and put them in one of the two tubes and sign it as test tube .
3. Withdraw 20µ of uric acid standard and put them in the other tube and sign it as standard tube .
4. Leave the two tubes in water bath for 5 minutes or in room temperature for 10 minutes .
5. Use the wave length 546 nm for measuring.
6. Put the standard and record the reading then put the tested serum and record the reading.
Calculation:
[The reading of test / The reading of standard ] * conc. of UA standard (usually 6 or 5 mg/dl) .
Normal values:
♂ : 3.4 – 7.0 mg/dl
♀ : 2.4 – 5.7 mg/dl
Creatinine analysis
Procedure:
-In Blood
Sample serum or plasma
The reagent usually must be prepared before use according to kits of the chemicals.
1.put 1 ml of working reagent in two test tubes.
2.put 100 µ of serum in one tube and read after exact 30 sec. abs1 at wave length 500 then wait for additional 2 minutes and read again abs2.
3.put 100 µ of standard in the other tube read after exact 30 sec. abs1 then wait for additional 2 minutes and read again abs2.
Calculation:
abs of sample (abs2 - abs1) / abs of standard (abs2 - abs1) * 2 = .......mg / dl
-In urine
the urine must be collected for 24 hrs. then take 1ml urine and put on it 49 ml water then take from the solution 100 µ and repeat as shown above
Calculation:
abs of sample / abs of standard * 100 = ....... mg / dl.
Normal values
in serum or plasma 0.6 - 1.4 mg / dl
in urine 1 - 1.5 mg / dl
-In Blood
Sample serum or plasma
The reagent usually must be prepared before use according to kits of the chemicals.
1.put 1 ml of working reagent in two test tubes.
2.put 100 µ of serum in one tube and read after exact 30 sec. abs1 at wave length 500 then wait for additional 2 minutes and read again abs2.
3.put 100 µ of standard in the other tube read after exact 30 sec. abs1 then wait for additional 2 minutes and read again abs2.
Calculation:
abs of sample (abs2 - abs1) / abs of standard (abs2 - abs1) * 2 = .......mg / dl
-In urine
the urine must be collected for 24 hrs. then take 1ml urine and put on it 49 ml water then take from the solution 100 µ and repeat as shown above
Calculation:
abs of sample / abs of standard * 100 = ....... mg / dl.
Normal values
in serum or plasma 0.6 - 1.4 mg / dl
in urine 1 - 1.5 mg / dl
Urea
Procedure :
1.prepare two test tubes mark one as test tube and the other is standard tube .
2.in standard tube put : 1 ml buffer + one drop urease (R2) + 10 µ standard reagent (R1) leave for 5 min. in room temp.
3.in test tube put at same time : 1 ml buffer + one drop urease (R2) + 10 µ serum or plasma then leave for 5 min in room temp.
4.then put 200 µ of Reagent 4 (R4) and leave for 5 min. in water bath or 10 min. in room temp.
5.Measure at 580 wave length.
Calculation :
[ reading test / reading standard ] x 50 =.......mg / dl . OR [ reading test / reading standard ] x 8.33 =......mmol /l
Normal values:
15 - 45 mg / dl.
OR
2.5 - 7.5 mmol / l.
1.prepare two test tubes mark one as test tube and the other is standard tube .
2.in standard tube put : 1 ml buffer + one drop urease (R2) + 10 µ standard reagent (R1) leave for 5 min. in room temp.
3.in test tube put at same time : 1 ml buffer + one drop urease (R2) + 10 µ serum or plasma then leave for 5 min in room temp.
4.then put 200 µ of Reagent 4 (R4) and leave for 5 min. in water bath or 10 min. in room temp.
5.Measure at 580 wave length.
Calculation :
[ reading test / reading standard ] x 50 =.......mg / dl . OR [ reading test / reading standard ] x 8.33 =......mmol /l
Normal values:
15 - 45 mg / dl.
OR
2.5 - 7.5 mmol / l.
Nov 18, 2010
Brucellosis
Definition:
Brucellosis is a serious bacterial disease that causes fever, joint pain and fatigue. Brucella, the bacteria that cause brucellosis, spread from animals to people, often via unpasteurized milk, cheese and other dairy products.
Also known as Mediterranean fever or undulant fever, brucellosis is uncommon in the United States. Worldwide, brucellosis affects hundreds of thousands of people and animals in Mediterranean countries and other areas each year. The bacteria can spread through the air or through direct contact with infected animals.
Brucellosis can usually be treated successfully with antibiotics. Treatment takes several weeks, however, and relapses are common. Avoiding unpasteurized dairy products and taking precautions when working with animals or in a laboratory can help prevent brucellosis. Animals can be vaccinated against the disease.
Symptoms
Symptoms of brucellosis may show up anytime from a few days to a few months after you're infected with brucella, the bacteria that cause brucellosis. Signs and symptoms are similar to those of the flu and include:
- Fever, often rising to 104 F (40 C) or more in the afternoon — a rising and falling (undulating) fever is one of the hallmarks of the disease
- Chills
- Sweats
- Weakness
- Fatigue
- Joint, muscle and back pain
- Headache
Brucellosis symptoms may disappear for weeks or months and then return. In some people, brucellosis becomes chronic, with symptoms persisting for years, even after treatment. Long-term signs and symptoms include fatigue, fevers, arthritis and spondylitis — an inflammatory arthritis that affects the spine and nearby joints.
When to see a doctor
Brucellosis can be hard to identify, especially in the early stages, when it often resembles the flu. See your doctor if you develop a rapidly rising fever, muscle aches or unusual weakness and have any risk factors for the disease, or if you have a persistent fever.
Brucellosis can be hard to identify, especially in the early stages, when it often resembles the flu. See your doctor if you develop a rapidly rising fever, muscle aches or unusual weakness and have any risk factors for the disease, or if you have a persistent fever.
Causes:
Brucellosis affects many wild and domestic animals. Cattle, goats, sheep, pigs, dogs, camels, wild boar and reindeer are especially prone to the disease. A form of brucellosis also affects harbor seals, porpoises and certain whales.
At least six species or strains of bacteria cause brucellosis in animals, but not all produce illness in humans. The bacteria spread from animals to people in three main ways:
- Raw dairy products. Brucella bacteria in the milk of infected animals can spread to humans in unpasteurized milk, ice cream, butter and cheeses. The bacteria can also be transmitted in raw or undercooked meat from infected animals.
- Inhalation. Brucella bacteria spread easily in the air. Farmers, laboratory technicians and slaughterhouse workers can inhale the bacteria.
- Direct contact. Bacteria in the blood, semen or placenta of an infected animal can enter your bloodstream through a cut or other wound. Because normal contact with animals — touching, brushing or playing — doesn't cause infection, people rarely get brucellosis from their pets. Even so, people with weakened immune systems should avoid handling dogs known to have the disease.
Brucellosis normally doesn't spread from person to person, but in a few cases, women have passed the disease to their infants during birth or through their breast milk. Rarely, brucellosis may spread through sexual activity or through contaminated blood or bone marrow transfusions.
Complications
By Mayo Clinic staff Brucellosis can affect almost any part of your body, including your reproductive system, liver, heart and central nervous system. Chronic brucellosis may cause complications in just one organ or throughout your body. Possible complications include:
- Infection of the heart's inner lining (endocarditis). This is one of the most serious complications of brucellosis. Untreated endocarditis can damage or destroy the heart valves and is the leading cause of brucellosis-related deaths.
- Arthritis. Osteoarthritis is marked by pain, stiffness and swelling in your joints, especially the knees, hips, ankles, wrists and spine. Spondylitis — inflammation of the joints between the bones (vertebrae) of your spine or between your spine and pelvis — can be particularly hard to treat and may cause lasting damage.
- Inflammation and infection of the testicles (epididymo-orchitis). The bacteria that cause brucellosis can infect the epididymis, the coiled tube that connects the vas deferens and the testicle. From there, the infection may spread to the testicle itself, causing swelling and pain, which may be severe. Brucellosis can also affect the prostate gland and kidneys.
- Anemia. Anemia, in which you don't have enough healthy red blood cells, can cause pale skin, fatigue and shortness of breath.
- Skin rashes. Rashes and other skin problems are a rare complication of brucellosis.
- Miscarriage. Brucellosis may cause early pregnancy loss in some women.
- Hepatitis. Brucellosis can cause this serious liver disease, which, if not treated, can lead to liver scarring (cirrhosis) and ultimately to liver failure.
- Central nervous system infections. These include potentially life-threatening illnesses such as meningitis, an inflammation of the membranes surrounding the brain and spinal cord, and encephalitis, inflammation of the brain itself.
Treatments and drugs
By Mayo Clinic staff Treatment for brucellosis aims to relieve symptoms, prevent a relapse of the disease and avoid complications. You'll need to take medications for at least six weeks, and your symptoms may not go away completely for several months. The disease can also return and may become chronic.
Antibiotics
The standard treatment for brucellosis is a combination of two or three antibiotic medications, usually doxycycline in combination with streptomycin, rifampin or gentamicin. You'll take these drugs for six weeks or longer. If brucellosis has affected your central nervous system, you may need to take three antibiotics for as long as three months. Children and pregnant women can't take certain antibiotics, so their treatment may involve just one antibiotic or a different combination of drugs.
The standard treatment for brucellosis is a combination of two or three antibiotic medications, usually doxycycline in combination with streptomycin, rifampin or gentamicin. You'll take these drugs for six weeks or longer. If brucellosis has affected your central nervous system, you may need to take three antibiotics for as long as three months. Children and pregnant women can't take certain antibiotics, so their treatment may involve just one antibiotic or a different combination of drugs.
Nov 16, 2010
WIDAL TEST ( simple steps)
Widal test is a tube agglutination test employed in the serological diagnosis of enteric fever. The test is named after
Georges Fernand Isidore Widal, a French physician and bacteriologist, born March 9, 1862, Algeria; died January
14, 1929, Paris.
Principle: Patients’ suffering from enteric fever would possess antibodies in their sera which can react and
agglutinate serial doubling dilutions of killed, coloured Salmonella antigens in a tube agglutination test.
Requirements: Widal rack, round-bottomed Felix tubes, conical-bottomed Dreyer’s tubes, water bath, doubly
diluted patient serum in three-four rows, Killed coloured suspensions of S.typhi O antigen, S.typhi H antigen,
S.paratyphi AH antigen and optionally S.paratyphi BH antigen.
Preparation of antigens: Salmonella typhi 901 strain is used to prepare S.typhi O and S.typhi H antigens. O
antigens for S.paratyphi A and S.paratyphi B are not taken as they cross-react with S.typhi O antigen. H antigen
suspension is prepared by treating overnight broth culture or saline suspension of Salmonella with 0.1% formalin.
For preparing O antigen suspension, Salmonella are grown on phenol agar (1:800) to inhibit flagella. The growth is
then emulsified in small volume of saline, mixed with 20 times its volume of alcohol, heated at 40oC to 50oC for 30
minutes and centrifuged. The antigens are treated with chloroform (preservative) and appropriate dyes are added
for easy identification of antigens.
Procedure:
© Sridhar Rao P.N (www.microrao.com)
Patient serum is doubly diluted by mixing and transferring from 1:10 to 1:640 in three-four rows. First row usually
comprises of Felix tubes, where somatic S.typhi O antigen is added. For all the remaining rows, Dreyer’s tubes are
taken; where different flagellar H antigens are added. Each tube must contain 0.5ml of diluted serum. A test tube
with only saline is kept in each row as control. All the tubes (including control) in a row are mixed with 0.5ml of
antigen suspension. The first row is treated with S.typhi O antigen, the second row with S.typhi H antigen, the third
row with S.paratyphi AH antigen and the fourth row with S.paratyphi BH antigen. Since infections by S.paratyphi B
are rare, this antigen is usually omitted in the test. After all the tubes have been treated with specific antigen
suspensions, the widal rack is placed in a thermostatically controlled water bath maintained at 37oC for overnight
incubation. Another approach is to incubate the tubes at 50-55oC.
Reading the results: The control tubes must be examined first, where they should give no agglutination. The
agglutination of O antigen appears as a “matt” or “carpet” at the bottom. Agglutination of H antigens appears loose,
wooly or cottony. The highest dilution of serum that produces a positive agglutination is taken as titre. The titres for
all the antigens are noted.
Slide widal test:
A slide widal test is more popular among diagnostic laboratories as it gives rapid results.
Qualitative test: One drop each of undiluted patients’ serum samples for the four antigens are placed on the circled
card and one drop of each of the four Salmonella antigens are added separately and gently rotated for one minute.
Appearance of agglutination gives qualitative results. To know the titre for each of the antigens, the test is repeated
with dilutions of serum.
Quatitative test: 80 µl, 40 µl, 20 µl, 10 µl and 5 µl of patient’s serum each for the four antigens are placed on the
circled card. To each series of serum specimen, one drop of specific antigen is added to each, mixed and rotated
for one minute. Agglutination in each of these is noted. 80 µl corresponds to 1in 20 dilution, 40 µl to 1 in 40, 20 µl to
1 in 80, 10 µl to 1 in 160 and 5 µl corresponds to 1 in 320 titre.
Interpretation of widal test:
Timing of test is important, as antibodies begin to arise during end of first week. The titres increase during
second, third and fourth week after which it gradually declines. The test may be negative in early part of first
week.
Single test is usually of not much value. A rise in titre between two sera specimens is more meaningful than
a single test. If the first sample is taken late in the disease, a rise in titre may not be demonstrable. Instead,
there may be a fall in titre.
Baseline titre of the population must be known before attaching significance to the titres. The antibody
levels of individuals in a population of a given area give the baseline titre. A titre of 100 or more for O
antigen is considered significant and a titre in excess of 200 for H antigens is considered significant.
Patients already treated with antibiotics may not show any rise in titre, instead there may be fall in titre.
Patients treated with antibiotics in the early stages may not give positive results.
Patients who have received vaccines against Salmonella may give false positive reactions. This can be
differentiated from true infection by repeating the test after a week. True untreated infection results in rise in
titre whereas vaccinated individuals don’t demonstrate any rise in titre.
Those individuals, who had suffered from enteric fever in the past, sometimes develop anti-Salmonella
antibodies during an unrelated or closely related infection. This is termed anamnestic response and can be
differentiated from true infection by lack of any rise in titre on repetition after a week.
Antigen suspensions with fimbrial antigens may sometimes give false positive reactions due to sharing of
fimbrial antigens by some Enterobacteriaceae members. Antigen suspension must be devoid of fimbrial
antigens.
* Widal test is losing its relevance in Western and European nations but continues to be used in India.
Georges Fernand Isidore Widal, a French physician and bacteriologist, born March 9, 1862, Algeria; died January
14, 1929, Paris.
Principle: Patients’ suffering from enteric fever would possess antibodies in their sera which can react and
agglutinate serial doubling dilutions of killed, coloured Salmonella antigens in a tube agglutination test.
Requirements: Widal rack, round-bottomed Felix tubes, conical-bottomed Dreyer’s tubes, water bath, doubly
diluted patient serum in three-four rows, Killed coloured suspensions of S.typhi O antigen, S.typhi H antigen,
S.paratyphi AH antigen and optionally S.paratyphi BH antigen.
Preparation of antigens: Salmonella typhi 901 strain is used to prepare S.typhi O and S.typhi H antigens. O
antigens for S.paratyphi A and S.paratyphi B are not taken as they cross-react with S.typhi O antigen. H antigen
suspension is prepared by treating overnight broth culture or saline suspension of Salmonella with 0.1% formalin.
For preparing O antigen suspension, Salmonella are grown on phenol agar (1:800) to inhibit flagella. The growth is
then emulsified in small volume of saline, mixed with 20 times its volume of alcohol, heated at 40oC to 50oC for 30
minutes and centrifuged. The antigens are treated with chloroform (preservative) and appropriate dyes are added
for easy identification of antigens.
Procedure:
© Sridhar Rao P.N (www.microrao.com)
Patient serum is doubly diluted by mixing and transferring from 1:10 to 1:640 in three-four rows. First row usually
comprises of Felix tubes, where somatic S.typhi O antigen is added. For all the remaining rows, Dreyer’s tubes are
taken; where different flagellar H antigens are added. Each tube must contain 0.5ml of diluted serum. A test tube
with only saline is kept in each row as control. All the tubes (including control) in a row are mixed with 0.5ml of
antigen suspension. The first row is treated with S.typhi O antigen, the second row with S.typhi H antigen, the third
row with S.paratyphi AH antigen and the fourth row with S.paratyphi BH antigen. Since infections by S.paratyphi B
are rare, this antigen is usually omitted in the test. After all the tubes have been treated with specific antigen
suspensions, the widal rack is placed in a thermostatically controlled water bath maintained at 37oC for overnight
incubation. Another approach is to incubate the tubes at 50-55oC.
Reading the results: The control tubes must be examined first, where they should give no agglutination. The
agglutination of O antigen appears as a “matt” or “carpet” at the bottom. Agglutination of H antigens appears loose,
wooly or cottony. The highest dilution of serum that produces a positive agglutination is taken as titre. The titres for
all the antigens are noted.
Slide widal test:
A slide widal test is more popular among diagnostic laboratories as it gives rapid results.
Qualitative test: One drop each of undiluted patients’ serum samples for the four antigens are placed on the circled
card and one drop of each of the four Salmonella antigens are added separately and gently rotated for one minute.
Appearance of agglutination gives qualitative results. To know the titre for each of the antigens, the test is repeated
with dilutions of serum.
Quatitative test: 80 µl, 40 µl, 20 µl, 10 µl and 5 µl of patient’s serum each for the four antigens are placed on the
circled card. To each series of serum specimen, one drop of specific antigen is added to each, mixed and rotated
for one minute. Agglutination in each of these is noted. 80 µl corresponds to 1in 20 dilution, 40 µl to 1 in 40, 20 µl to
1 in 80, 10 µl to 1 in 160 and 5 µl corresponds to 1 in 320 titre.
Interpretation of widal test:
Timing of test is important, as antibodies begin to arise during end of first week. The titres increase during
second, third and fourth week after which it gradually declines. The test may be negative in early part of first
week.
Single test is usually of not much value. A rise in titre between two sera specimens is more meaningful than
a single test. If the first sample is taken late in the disease, a rise in titre may not be demonstrable. Instead,
there may be a fall in titre.
Baseline titre of the population must be known before attaching significance to the titres. The antibody
levels of individuals in a population of a given area give the baseline titre. A titre of 100 or more for O
antigen is considered significant and a titre in excess of 200 for H antigens is considered significant.
Patients already treated with antibiotics may not show any rise in titre, instead there may be fall in titre.
Patients treated with antibiotics in the early stages may not give positive results.
Patients who have received vaccines against Salmonella may give false positive reactions. This can be
differentiated from true infection by repeating the test after a week. True untreated infection results in rise in
titre whereas vaccinated individuals don’t demonstrate any rise in titre.
Those individuals, who had suffered from enteric fever in the past, sometimes develop anti-Salmonella
antibodies during an unrelated or closely related infection. This is termed anamnestic response and can be
differentiated from true infection by lack of any rise in titre on repetition after a week.
Antigen suspensions with fimbrial antigens may sometimes give false positive reactions due to sharing of
fimbrial antigens by some Enterobacteriaceae members. Antigen suspension must be devoid of fimbrial
antigens.
* Widal test is losing its relevance in Western and European nations but continues to be used in India.
Widal test
The Widal test is a presumptive serological test for enteric fever or undulant fever. In case of Salmonella infections, it is a demonstration of agglutinating antibodies against antigens O-somatic and H-flagellar in the blood. For brucellosis, only O-somatic antigen is used.
The Widal test is not a very specific test, since patients are often exposed to other bacteria (e.g. Salmonella enteritidis, Salmonella typhimurium and some types of E. coli) in this species that induce cross-reactivity; many people have antibodies against these enteric pathogens, which also react with the antigens in the Widal test, causing a false-positive result. Test results need to be interpreted carefully in the light of past history of enteric fever, typhoid vaccination, and the general level of antibodies in the populations in endemic areas of the world. Typhidot is the other test used to ascertain the diagnosis of typhoid fever. As with all serological tests, the rise in antibody levels needed to make the diagnosis takes 7-14 days, which limits. Other means of diagnosing Salmonella typhi (and paratyphi) include cultures of blood, urine and faeces. The organism also produces H2S from thiosulfate.
Often 2-mercaptoethanol is added. This agent more easily denatures the IgM class of antibodies, so if a decrease in the titer is seen after using this agent, it means that the contribution of IgM has been removed leaving the IgG component. This differentiation of antibody classes is important; as it allows for the distinction of a recent (IgM) from an old infection (IgG)
The Widal test is positive if TO antigen titer is more than 1:160 in an active infection, or if TH antigen titer is more than 1:160 in past infection or in immunized persons. A single Widal test is of little clinical relevance due to the number of cross reacting infections, including malaria. If no other tests (either bacteriologic culture or more specific serology) are available, a four fold increase in the titer (e.g., from 1:40 to 1:160) in the course of the infection, or a conversion from an IgM reaction to an IgG reaction of at least the same titer, would be consistent with a typhoid infection.
The Widal test is "a test involving agglutination of typhoid bacilli when they are mixed with serum containing typhoid antibodies from an individual having typhoid fever; which may be used to detect the presence of Salmonella typhi and S. paratyphi
Testing the Stool Sample
In general, the results of stool tests are usually reported back within 3 to 4 days, although it often takes longer for parasite testing to be completed.
Examining the Stool for Blood
Your doctor will sometimes check the stool for blood, which can be caused by certain kinds of infectious diarrhea, bleeding within the gastrointestinal tract, and other conditions. However, most of the time, blood streaking in the stool of an infant or toddler is from a slight rectal tear, called a fissure, which is caused by straining against a hard stool (this is fairly common in infants and kids with ongoing constipation).
Testing for blood in the stool is often performed with a quick test in the office that can provide the results immediately. First, stool is smeared on a card, then a few drops of a developing solution are placed on the card. An instant color change shows that blood is present in the stool. Sometimes, stool is sent to a laboratory to test for blood, and the result will be reported within hours.
Culturing the Stool
Stool can be cultured for disease-causing bacteria. A stool sample is placed in an incubator for at least 48 to 72 hours and any disease-causing bacteria are identified and isolated. Remember that not all bacteria in the stool cause problems; in fact, about half of stool is bacteria, most of which live there normally and are necessary for digestion. In a stool culture, lab technicians are most concerned with identifying bacteria that cause disease.
For a stool culture, the lab will need a fresh or refrigerated sample of stool. The best samples are of loose, fresh stool; well-formed stool is rarely positive for disease-causing bacteria. Sometimes, more than one stool will be collected for a culture.
Swabs from a child's rectum also can be tested for viruses. Although this is not done routinely, it can sometimes give clues about certain illnesses, especially in newborns or very ill children. Viral cultures can take a week or longer to grow, depending on the virus.
Testing the Stool for Ova and Parasites
Stool may be tested for the presence of parasites and ova (the egg stage of a parasite) if a child has prolonged diarrhea or other intestinal symptoms. Sometimes, the doctor will collect two or more samples of stool to successfully identify parasites. If parasites — or their eggs — are seen when a smear of stool is examined under the microscope, the child will be treated for a parasitic infestation. The doctor may give you special collection containers that contain chemical preservatives for parasites.
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