Bilirubin test and concentration in blood

Bilirubin is a waste product resulting from the lysis of red blood cells and the release of hemoglobin. The heme (iron) portion of the hemoglobin molecule is converted into the bile pigment bilirubin . Bilirubin is a yellow pigment. An abnormally increased blood concentration creates a jaundiced discoloration of the skin, whites of the eyes, and mucous membranes.
Bilirubin is eliminated from the body through a complex process involving the liver. 

There are two main forms of bilirubin: indirect or unconjugated
bilirubin, which is transported to the liver as a bilirubin-albumin
complex and converted to direct or conjugated bilirubin that is eventually excreted in feces and urine. 

Liver malfunction can inhibit this process . Consequently bilirubin will not be converted to excretable products and will accumulate
in the blood.
Bilirubin testing can include measuring the levels of indirect bilirubin, direct bilirubin, and total bilirubin, the sum of direct and indirect bilirubin.

Normal Range

Total bilirubin
0.2-1 .0 mg/dl

Indirect bilirubin
0.1-0.7 mg/dl

Direct bilirubin
0.1-0.3 mg/dl

Newborn total bilirubin
1-12 mg/dl

Diagnostic Application

Destruction of RBCs; liver dysfunction Liver and kidney functions
Kidney excretory function; decreased muscle mass Diagnostic for gout

Variations from Normal. 

Elevated indirect bilirubin is usually associated with increased destruction of red blood cells, destruction of hemoglobin as seen in hemolytic anemias, pernicious anemia, sickle cell anemia, transfusion reactions, and hemolytic disease of newborns.
Abnormally elevated indirect bilirubin concentrations may also indicate liver dysfunction in that the liver is unable to convert indirect bilirubin to direct bilirubin. Hepatic diseases associated with elevated indirect bilirubin include hepatitis, cirrhosis, and extensive liver tumors.
An increase in direct bilirubin levels usually indicates an inability to excrete bilirubin . Gallstones, tumors, bile duct obstruction, and cancer of the pancreatic head can cause increases in direct bilirubin.

Interfering Circumstances. 

Improper handling of the blood sample can alter test results . Exposure of the specimen to sunlight or high-intensity artificial
light at room temperature will decrease bilirubin concentration .
Shaking the blood specimen and the presence of air bubbles may also decrease bilirubin levels.
Drugs that cause increased bilirubin include allopurinol, anabolic
steroids, ascorbic acid, diabinese, codeine, steroids, diuretics, and oral contraceptives
. Drugs associated with decreased levels are barbiturates, caffeine,
penicillin, and high doses of salicylates.

Triglyceride

Triglycerides, the main form of stored fat in humans, are an important source of energy. Triglycerides exists in the bloodstream and are transported throughout the body by VLDLs and LDLs. Excess plasma triglycerides are stored in the body's adipose tissue .
Measurement of triglyceride levels is part of the lipid profile . The triglyceride test is used to evaluate the individual's risk of coronary and vascular disease, and to identify atherosclerosis. The test can also provide information about the body's ability to metabolize fat.

Normal Range. 

 

Variations in triglyceride ranges are affected by gender,

age, and diet.

Men
40-190 mg/dl

Women
35-160 mg/dl

Children
30-100 mg/dl

Variations from Normal. 

Elevated triglyceride levels increase the individual's risk of atherosclerosis, ASHD, and peripheral vascular disease. 

Other clinical conditions associated with increased triglycerides include all types of hyperlipidemia, poorly controlled diabetes, pancreatitis, kidney syndromes, and toxemia. Individuals with a history of myocardial infarction may show increased triglycerides for up to one year postinfarction .

A highcarbohydrate diet may contribute to high triglyceride levels.
Decreased triglyceride values are seldom seen as a clinical problem.
Genetic defects and chronic problems of malnutrition and malabsorption syndrome will exhibit decreased triglyceride levels. Other diseases associated with low triglycerides are chronic obstructive pulmonary disease, brain infarction, and hyperthyroidism.

Interfering Circumstances. 

 A temporary increase in triglycerides can be triggered by alcohol consumption and a pretest meal high in fats. Pregnancy, oral contraceptives, and estrogen are also associated with elevated values.
Drugs that may decrease triglyceride levels include ascorbic acid, the antitumor enzyme asparaginase, and lipid-lowering agents such as clofibrate.

Very-Low-Density Lipoprotein (VLDL); Low-Density Lipoprotein (LDL)

Very-low-density lipoproteins (VLDLs) are plasma proteins composed primarily of triglycerides and small amounts of cholesterol. The VLDLs transport triglycerides from the liver to the peripheral tissue.

The breakdown of VLDLs is a major source of low-density lipoproteins (LDLs), which are cholesterol-rich plasma proteins. Increased levels of very-low-density lipoprotein is accompanied by increased levels of low-density lipoproteins .
Very-low-density lipoproteins are associated with atherosclerosis, but not to the same degree as low-density lipoproteins .
Low-density lipoprotein, a primary transporter of cholesterol, delivers and deposits the cholesterol into the peripheral tissues. Because of this function, LDLs are sometimes referred to as "bad" cholesterol and are associated with atherosclerosis, ASHD, and peripheral vascular disease.

The VLDL and LDL levels are mathematical calculations that utilize the total cholesterol, triglyceride, and HDL values. The VLDL is usually expressed as a percentage of the total blood cholesterol . The LDL is deter mined by subtracting the HDL minus one-fifth of the triglyceride level from the total cholesterol . 

The VLDL and LDL levels can be calculated manually or as part of an automated lipid profile test.

Normal Range

Low-density lipoprotein
60-180 mg/dl

Very-low-density lipoprotein
25-50% of total cholesterol level

Variations from Normal. Elevated LDL levels increase the individual's risk for ASHD and peripheral vascular disease. Other diseases associated with increased LDLs include type IIA familial hyperlipidemia, multiple myeloma, hypothyroidism, kidney and liver syndromes, and diabetes.
Increased VLDL levels are primarily caused by type IV hyperlipidemia, a common form of increased lipoproteins that is sometimes familial. Type IV hyperlipidemia is also called endogenous hypertriglyceridemia. Other dis eases associated with elevated VLDDs include alcoholism, obesity, diabetes mellitus, chronic renal disease, and pancreatitis . A diet rich in fatty foods and animal fats may also elevate LDL and VLDL levels. Malnutrition and malabsorption syndromes will result in decreased LDL and VLDL levels.

Interfering Circumstances. Very-low-density lipoprotein and low-density lipoprotein results can be altered by binge eating. Drugs that increase lipoprotein levels include oral contraceptives, estrogen, progestin, and steroids.

High-Density Lipoprotein (HDL)

High-density lipoproteins (HDL) are plasma proteins that function as carriers of plasma cholesterol . Measuring the cholesterol contained in the HDL molecule is predictive of the individual's risk for coronary artery disease . 

It is believed that the HDL molecule carries cholesterol from the peripheral tissues of the body to the liver, where the cholesterol is converted into bile acids and eventually excreted. Cholesterol that is part of the high-density lipoprotein molecule will not be deposited in blood vessel walls. Because of this, HDL is sometimes referred to as the "good" cholesterol and is believed to have a protective effect on the circulatory system.

Normal Range

 

Men
>45 mg/dl
Women
>55 mg/dl

Variations from Normal. Some variations in high-density lipoprotein levels are based on gender and age. Increases in HDL levels are not often seen as problematic. However, since the liver is responsible for the metabolism of HDL, a nontherapeutic elevation of HDL levels can signify liver disease.
Most individuals are more concerned about low HDL levels.
Decreased availability of high-density lipoproteins may leave more cholesterol free to be deposited in the peripheral tissue of the body. Low levels of HDLs increase the risk of ASHD.

Interfering Circumstances. Lifestyle factors that influence HDL levels include smoking and alcohol ingestion, which decreases HDLs. Exercise can raise HDL levels. Drugs that may cause a lipoprotein increase are aspirin, oral contraceptives, steroids, and sulfonamides.

Cholesterol test in blood

cholesterol is one of the most tested lipids in the body, cholesterol is sometimes only associated with arteriosclerotic vascular disease.

Cholesterol, however, is an important component of the body and is necessary for the production of bile acids, steroids, and cellular membranes. In addition, cholesterol plays a role in maintaining the skin's resistance to water-soluble substances and prevents excess evaporation of water from the body.

About 75% of cholesterol is transported in the bloodstream via low density lipoproteins, and the remaining 25% is bound to high-density
lipoproteins. In the past, blood cholesterol was reported only as total
cholesterol.

Current laboratory practices include the measurement of high-density lipoproteins, low-density lipoproteins, and very-low-density lipoproteins.

Normal Ranges. Normal ranges of cholesterol will vary with age, diet, and geographic location. Since there are many variables that affect plasma cholesterol levels, most references give a desirable range based primarily on age.

Under most circumstances, an upper limit of 200 mg/dl or less is desirable.

Adult/elderly
less than 200 mg/dl
Children
120-200 mg/dl
Infant
70-175 mg/dl
Newborn
53-135 mg/dl

Variations from Normal. High levels of cholesterol are associated with atherosclerosis and an increased risk of coronary artery disease . 

Other diseases linked to elevated cholesterol include uncontrolled diabetes, obesity, and hypothyroidism.

Type II familial hypercholesterolemia is an inherited disorder characterized by high levels of plasma cholesterol and early evidence
of atherosclerosis.

Hyperlipidemia type IIA is another name for type II familial hypercholesterolemia .
Decreased levels of cholesterol occur when cholesterol is not absorbed from the gastrointestinal tract as in malabsorption syndromes, liver disease, hyperthyroidism, anemia, and sepsis. 

Other conditions associated with decreased cholesterol include pernicious anemia, hemolytic jaundice, severe infections, and terminal stages of debilitating diseases such as cancer.

Interfering Circumstances. Pregnancy and removal of the ovaries will cause elevated cholesterol results. Drugs that cause an increased cholesterol level include adrenocorticotropic hormone, anabolic steroids, oral contraceptives, Dilantin, diuretics, and vitaminD. 

Decreased cholesterol levels are associated with drugs like allopurinol, androgens, erythromycin, Mevacor, niacin, and nitrates.

Insulin

Insulin, a hormone secreted by pancreatic beta cells,regulates metabolism of carbohydrates and is responsible for maintaining a constant blood glucose level. 
Insulin lowers blood glucose levels by promoting the transport of glucose from the bloodstream into the cells.
Insulin levels can be measured by radioimmunoassay, a technique that uses radioactive substances to determine the concentration of specific blood constituents .
Insulin levels are reported as microunits per milliliter (gU/mL).

Normal Range

4-20 gU/mL

Variations from Normal. Diseases such as acromegaly, Cushing's syndrome, and insulinoma (a benign tumor of the insulin secreting cells of the pancreas) are associated with an increased level of insulin. Decreased insulin levels are seen primarily in diabetes.

Interfering Circumstances. Food intake and obesity may cause false increases in insulin levels. Recent administration of radioisotopes may affect test results, as will use of oral contraceptives. Other drugs that may cause increased insulin levels include corticosteroids and levodopa.

C-Peptide and Glucagon

       C-peptide 

    C-peptide is formed in the islets of Langerhans, specifically the beta cells of the pancreas during insulin production. Since insulin and C-peptide are secreted into the bloodstream in near equal amounts, measuring C-peptide levels provides a reliable indication of blood insulin levels. The C-peptide test is also used to assess the secretory function of the beta cells, and to identify individuals who may be injecting insulin for nontherapeutic reasons.

    C-peptide levels are reported as nanogram per milliliter (ng/mL).
The C-peptide test is particularly helpful in measuring blood insulin
levels in diabetic patients who have developed insulin antibodies as a result of being treated with pork or bovine insulin. C-peptide is not affected by the presence of insulin antibodies.

Normal Range

0.78-1.89 ng/rnL

Variations from Normal. Increased C-peptide levels are associated with insulinoma, a benign tumor of the beta cells of the pancreas that causes the excessive secretion of insulin. Since most C-peptide is degraded in the kidney, renal failure results in elevated C-peptide levels.
Decreased C-peptide levels are associated with a radical pancreatectomy and diabetes mellitus. Fictitious hypoglycemia, hypoglycemia caused by secretive injection of insulin, can be identified via decreased levels of Cpeptide.
Interfering Circumstances. Obesity and oral hypoglycemic medications or agents may alter C-peptide test results .

Glucagon 

 

       Glucagon  a hormone secreted by pancreatic alpha cells, assists in the maintenance of blood glucose levels. When blood glucose levels decrease, glucagon stimulates the conversion of glycogen into glucose, which results in an increase in blood glucose . Glycogen, the stored form of glucose, is found primarily in the liver. Measuring plasma glucagon levels assists in diagnosing pancreatic conditions and disorders. Glucagon levels are reported as picogram per milliliter (pg/mL).

Normal Range

50-200 pg/mL

Variations from Normal. Glucagon levels increase in the presence of acute pancreatitis, diabetes mellitus, severe diabetic ketoacidosis, and glucagonoma, a pancreatic alpha cell tumor. Since glucagon may be metabolized by the kidneys, chronic renal failure or kidney transplant rejection has the potential to cause increased glucagon levels . Decreased glucagon levels are associated with chronic pancreatitis, loss of pancreatic tissue, and idiopathic glucagon deficiency.

Interfering Circumstances . Lifestyle circumstances that may alter glucagon test results include prolonged fasting or moderate to heavy exercise.
Therapeutic interventions that alter glucagon test results consist of radioactive scans within forty-eight hours of testing; drugs such as insulin

Insulin and glucocorticoids that may increase glucagon levels; and drugs such as secretin and propranolol that may decrease glucagon levels.

Glucose Tolerance Test (GTT); Standard Oral Glucose Tolerance Test (SOGTT)

      

 

   The glucose tolerance test is a timed test of the glucose concentration in both the blood and urine.

This test is used to confirm or rule out diabetes and is a
definitive test for diagnosing hypoglycemia. After fasting overnight, the client is given a concentrated amount of glucose dissolved in a flavored, water-based drink. Blood and urine samples are collected over a three- to four-hour period.
In health, the insulin response is immediate and in sufficient quantity to tolerate the glucose load and to move the glucose from the blood to the cells of the body. There will be a minimal and temporary rise in plasma glucose levels within the first hour, with a return to normal levels in the second hour of testing .
 

Normal Range

Fasting
70-115 mg/dl
30 min
less than 200 mg/dl
1 hour
less than 200 mg/dl
2 hours
less than 140 mg/dl
3 hours
70-115 mg/dl
4 hours
70-115 mg/dl

Variations from Normal. Individuals who are diabetic or hypoglycemic will not be able to tolerate the glucose load administered during the glucose tolerance test. Diabetic clients will exhibit increased glucose levels that exceed 190 mg/dl at one hour; 165 mg/dl at two hours; or 145 mg/dl at three hours. Different types of diabetes can be identified by the glucose elevation at specific time intervals.
Type II or noninsulin-dependent diabetes mellitus (NIDDM), which is
characterized by a delay in the secretion of insulin or a decreased number of insulin receptor sites, displays an elevated glucose level until the two-hour point. Type I or insulin-dependent diabetes mellitus (IDDM), which may be characterized by a lack of insulin or the absence of its secretion, displays an elevated glucose level throughout the test period. Gestational diabetes also displays an elevated glucose level throughout the test period.
The hypoglycemic individual will also have trouble handling the glucose load administered during the glucose tolerance test. The glucose load will trigger high insulin levels, which will in turn mobilize the glucose to leave the blood. Consequently the blood glucose level will drop below normal at two hours, and remain low for the remainder of the test period. 

Interfering Circumstances. Circumstances surrounding the patient's lifestyle can interfere with test results. Smoking and exercise during the test period can stimulate glucose levels. Prolonged inactivity and weight reduction dieting prior to testing can produce inaccurate results.
Specific drugs and medications will interfere with glucose tolerance.
These include insulin, large doses of aspirin, oral contraceptives, estrogens, anti-inflammatory drugs, nicotine, lithium, and thiazide diuretics.

Postprandial Blood Sugar (PPBS); Two-Hour Postprandial Blood Sugar (2-hour PPBS)

    

While many practitioners use the fasting blood sugar test results as a primary screen for diabetes mellitus, the postprandial blood sugar test (PPBS) is often used to confirm the diagnosis . Prior to the test the client fasts overnight and then consumes a meal that contains approximately 100 grams
of carbohydrates, or drinks a special 100-gram carbohydrate drink. 

Two hours after eating, a venous blood sample is drawn and analyzed. The purpose of the PPBS test is to assess the body's response to the ingestion of carbohydrates in a meal. 


Like the fasting blood sugar test, the postprandial blood sugar test measures the plasma level of glucose. The value of the postprandial test is its ability to identify diabetic conditions that may not be clearly revealed by the fasting blood sugar test.

Normal Range

Age 50 or less                     70-140 mg/dl
Age 50-60                                  70-150 mg/dl
Age 60+                                      70-160 mg/dl

 

Variations from Normal.

 

A two-hour postprandial glucose level greater than 200 mg/dl is indicative of diabetes mellitus.

Interfering Circumstances. 
 
Diseases and conditions that affect the results of the fasting blood sugar test will also affect the postprandial blood sugar
test. Smoking during the test period can cause an increased glucose level.

Blood Glucose and Related Blood Sugar Tests

        Introduction

           Glucose, a simple sugar, is the main blood carbohydrate and a major source of energy for all cells. The fasting blood sugar (FBS), postprandial blood sugar (PPBS), and the glucose tolerance test (GTT), or standard oral glucose tolerance test (SOGTT), are three of the most frequently performed blood sugar tests and are used to determine the level of glucose in the blood. Variations in blood glucose levels are broadly categorized as hyperglycemia, or increased blood sugar levels, and hypoglycemia, or decreased blood sugar levels .

         Related blood sugar tests measure the body's ability to produce insulin and glucose . Insulin and glucose production can be monitored by measuring blood levels of C-peptide, the residue of insulin formation; glucagon, a hormone that stimulates the production of glucose ; and insulin, the hormone responsible for glucose metabolism.

    Fasting Blood Sugar (FBS)

          The fasting blood sugar test measures the plasma level of glucose . Results are reported as the number of milligrams per deciliter (mg/dl) of blood. The test is performed to detect any disorder of glucose metabolism, primarily diabetes, and is also used to assess the management of diabetes. As the name implies, the client must refrain from eating approximately four to twelve hours prior to the test. If the client is an insulin-dependent diabetic, both food and insulin can be withheld until the blood specimen is drawn.

Normal Range

Adults
70-115 mg/dl

Children
60-110 mg/dl

Newborns
30-80 mg/dl

       Variations from Normal.

An increase in blood glucose, hyperglycemia, usually indicates diabetes. Myocardial infarction, meningitis, or encephalitis, all of which produce acute stress in bodily processes, may also cause an elevated blood glucose level. Other conditions associated with hyperglycemia include an increased secretion of glucocorticoids from the adrenal glands as seen in Cushing's disease, pituitary and pancreatic adenomas, pancreatitis, hyperthyroidism, and chronic illness or inactivity. Hyperglycemia is sometimes seen during pregnancy and is called gestational diabetes. The condition is usually diagnosed during the latter half of the pregnancy and is caused by an increased secretion of the pla cental hormone lactogen. Lactogen can inhibit the action of insulin, thereby increasing the blood glucose level. Gestational diabetes presents a risk to the fetus and mother and must be closely monitored throughout the pregnancy.

Hypoglycemia, a decrease in blood glucose, is often caused by an overdose of insulin or skipping meals. Other causes of hypoglycemia include pancreatic islet cell malignancy, severe liver damage, hypothyroidism, cortisol deficiency, and pituitary hormone deficiency.

Interfering Circumstances . 

Many drugs can interfere with fasting blood sugar results. Steroids, particularly prednisone, and diuretics can significantly alter test results . Anesthesia, stress, and obesity may also affect blood glucose levels.

Phosphate (PO,); Phosphorus (P)

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.

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.

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

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.

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.

Normal Range
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.

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.

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.

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.

      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.

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.
 

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 .

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.

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 .

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.

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.

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.

Normal Range

Platelets
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.

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.

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.

Normal Range

Adults and Children
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.

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.

Normal Range
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 .

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.

Normal Range
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.

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.

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

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.

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.

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

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.

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.

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%

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).

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

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.