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.