Laboratory Tests

Descriptions of laboratory test that might be ordered by your medical provider include:

Below are descriptions of some common laboratory tests. For a more complete list and descriptions see MedlinePlus website.

Albumin:

An albumin test measures the amount of this specific protein in the blood. It provides a general index of overall health and nutrition. Measurements aid in the diagnosis of kidney and intestinal diseases.

Alkaline Phosphatase:

Alkaline phosphatase is an enzyme found primarily in the bones and the liver. It promotes chemical activities in the cells of these tissues. Injury to the bones or liver releases alkaline phosphatase into the blood. High levels of alkaline phosphatase in the blood may indicate damage done by alcohol abuse or a number of other diseases to the bones or liver.

ASO (Anti-streptolysin O titer):

ASO titer is a blood test to measure anti-streptolysin O (ASO) antibodies. This test is used to detect prior infection by Group A Streptococcus, the bacterium responsible for diseases such as glomerulonephritis, rheumatic fever, bacterial endocarditis, and scarlet fever. ASO testing demonstrates the presence of antibodies generated by the body against the enzyme streptolysin O, which is produced by the bacteria and which causes destruction of red blood cells. The ASO antibody may be detected in the blood for weeks or months after the primary infection has been eradicated.

AST and ALT:

AST and ALT are liver and muscle enzymes. They promote chemical activities in the cells of these tissues. Injury to the liver or the muscles releases AST and ALT into the blood. Elevated levels may indicate liver problems, hepatitis, excessive alcohol ingestion, muscle injury, or recent heart attack.

Basic Metabolic Panel (BMP):

This chemistry panel aids in the diagnosis and management of various illnesses and injuries. The BMP includes: carbon dioxide, chloride, creatinine, glucose, potassium, sodium, and BUN testing. See above for more details concerning the individual tests.

Bilirubin:

This test evaluates liver function and red blood cell condition. Physicians use bilirubin to diagnose and monitor jaundice, to help confirm a diagnosis of obstructed bile ducts, and to help determine the cause of anemia. High levels of bilirubin may indicate congenital enzyme deficiencies, liver damage, hemolytic anemia, or obstruction of bile ducts from stones or tumors.

Blood Urea Nitrogen (BUN):

BUN measures the amount of urea (a waste product) in the blood. Urea is formed during normal metabolism of protein and is normally excreted along in the urine. The kidneys are responsible for filtering the blood of waste products. Consequently, urea can build up in the blood if the kidneys become diseased. Physicians use urea as an index of kidney function - the higher the urea, the worse the kidney function. BUN can also rise from dehydration even when the kidneys function properly.

Calcium:

Calcium levels are controlled by the parathyroid glands and the kidneys. Calcium is found mostly in bones and is important for proper blood clotting as well as nerve and cell activity. Medications such as diuretics; inherited disorders relating to calcium handling in the kidneys; and excess parathyroid gland activity can result in elevated calcium levels. Metabolic disorders can cause low calcium levels.

Complete Blood Count (CBC):

A CBC provides several pieces of information about a person's state of health based on the content of certain components within the blood (white blood cells, red blood cells, hematocrit, etc.). The CBC is one of the most routinely performed laboratory tests. Physicians use it to screen for a wide variety of disorders, including: anemia, infection, blood diseases, excessive menstrual bleeding, internal bleeding, and problems with clotting.

Comprehensive Metabolic Panel (CMP):

This chemistry panel aids in the diagnosis and management of various illnesses and injuries. The CMP includes: glucose, BUN, creatinine, chloride, sodium, potassium, calcium, bilirubin, albumin, total protein, AST, alkaline phosphatase, and carbon dioxide.

Creatinine:

Creatinine is a waste product produced by the body during muscle metabolism. The kidneys are responsible for regulating the waste as well as chemical and water contents of the blood. Consequently, high levels of creatinine in the blood may indicate decreased kidney function.

Glucose Tolerance Test:

Physicians often suggest a glucose tolerance test when they suspect a patient has diabetes mellitus. In this condition, the pancreas produces little or no insulin. Insulin is a hormone that helps the body's tissues absorb glucose so it can be used as a source of energy. A person suffering from diabetes mellitus typically has higher levels of glucose in his/her blood and urine because the body's tissues cannot absorb it without sufficient amounts of insulin.

The test requires five blood and urine specimens which the technician analyzes for the presence of glucose. The procedure usually takes 3 hours but can last as long as 6 hours. The technician collects the first blood and urine samples after the patient has fasted for 12 hours. He/she then gives the patient a test load of glucose. This test load is usually in the form of a syrupy, sweet drink. The patient must consume the entire mixture in 5 minutes. The technician collects blood and urine samples at 30 minutes, 1 hour, 2 hours, and 3 hours after the patient finishes the test load.

Normal glucose levels peak at 160 to 180 mg within 30 to 60 minutes after the patient has consumed the glucose test dose. They return to fasting levels or lower within 2 to 3 hours. In normal tests glucose is not present in the urine throughout the testing procedure. If glucose levels appear lower than normal, the person may have hypoglycemia. Hypoglycemia refers to low blood sugar. This condition can be due to one of a number of conditions, including: bowel problems that interfere with absorbing the glucose into the body; certain hormone imbalances, such as a low thyroid hormone level; a pancreas that secretes too much insulin; or certain drugs in the patient's system that interfere with the test, such as caffeine. If glucose levels appear higher than normal, the person may have one of a number of conditions including: diabetes mellitus or high blood sugar; hormone imbalances such as a high level of cortisol, a hormone that promotes metabolism; damage to the pancreas that prevents the manufacturing or secretion of insulin; or certain drugs in the patient's system.

Glucose Whole Blood Test:

People with diabetes must monitor their blood sugar levels carefully and frequently in order to maintain the best health possible. A glucose blood test involves pricking a finger with a small needle and putting a drop of blood on a test strip. Either an electronic blood glucose meter determines and reads the results or the test strip is matched to a color chart that pairs different glucose levels with different colors.

International Normalized Ratio (INR) - A "protime," or prothrombin time, gauges liver function by measuring how well a person's blood clots. The liver makes proteins called clotting factors that help blood to coagulate. If the liver is failing then it stops making enough of these factors and the protime becomes prolonged. A normal protime is usually about 11-14 seconds. A protime is considered prolonged if it is more than 1.2 times the control time (16.8 seconds). The test involves pricking the patient's finger to draw blood. The blood is applied to a test strip and a small electronic device analyzes the blood sample. The machine determines whether the blood is in the appropriate clotting range.

This test varies from one lab to another and has essentially been improved by using the International Normalized Ratio (INR). The INR is calculated from the protime (PT) by dividing by a standard reference value. This modified PT allows the INR to be accurately compared from one lab to another which can be very important for individuals treated with anticoagulants. Most physicians use the INR to follow people treated with Coumadin (warfarin). The normal INR for a person not on medications is 1. The most common goal range for treatment with coumadin is 2.0 - 3.0, although there are many exceptions.

Lipid Profile:

Lipids are fatty substances found in all living organisms. Lipids perform a number of important functions in the body. Phospholipids represent a major component of the cell membrane. They limit the passage of water and water-soluble compounds through the membrane. Phospholipids act as a barrier that allows the cell to keep its contents separate from the outside environment.

Fats and oils, or triglycerides, represent another type of lipid that performs an important function in the body. An organism forms stores of triglycerides when it has excess energy available from food or from photosynthesis. The body breaks these stores down to yield energy when the organism needs it.

Lipids also serve as cholesterol transporters within the body. Cholesterol is a substance produced in the liver and found in many foods. Special lipoproteins combine with cholesterol and move throughout the body. The two important types of lipoproteins are: low-density (LDL) and high-density (HDL). LDL delivers cholesterol to the body. HDL removes cholesterol from the blood. Medical experts believe that LDL at high levels promotes atherosclerosis, whereas HDL may slow it.

Atherosclerosis involves the build-up of cholesterol in the arteries. The build-up reduces the arteries' inside diameter and restricts blood flow. Blood clotting which can cause a heart attack or stroke most often occurs at places in the arteries where plaques have collected. Consequently, people with high levels of cholesterol, especially LDL, have an increased risk of developing heart disease.

The best total cholesterol level is under 200. A level between 200 and 239 means you have some increased risk of heart attack or stroke. A cholesterol level of 240 or more means that you have an even greater risk. Lipoprotein levels (LDL and HDL) are also important, especially if heart disease runs in the family or if an individual has a high cholesterol level. If an individual's total cholesterol level appears high because of a high LDL level, he/she may have a higher risk for heart disease or stroke. If an individual's total level seems high only because of a high HDL level, he/she probably does not have an increased risk of heart disease, and may even have a decreased risk.

An LDL cholesterol level of less than 130 is best. An LDL level of 160 or higher means the individual has an increased risk for heart disease. An HDL cholesterol level of less than 35 puts him/her at higher risk for heart disease. An HDL level of 60 or above reduces the risk of heart disease.

Eating healthy, low cholesterol foods can help lower LDL levels. Exercise, quitting smoking, and losing weight can help increase HDL levels. In general, people should start having their cholesterol checked when they are 20 years old. After that, cholesterol checks should be done at least once every five years. However, depending on the height of an individual's cholesterol level, his/her doctor may recommend that he/she have cholesterol checks more frequently.

Lytes Panel:

Lytes stands for electrolytes. Electrolytes help to control fluid levels in the body as well as to maintain normal pH levels and the correct electric potential between nerve cells (the electric potential enables transmission of nerve signals throughout the body). Electrolytes include potassium, sodium, chloride, and carbon dioxide.

Potassium levels are controlled very carefully by the kidneys. Potassium helps the nerves and muscles, particularly the heart, to function properly. Any value outside the normal range, high or low, requires medical evaluation, especially if the patient is taking a diuretic (water pill) or heart pill (Digoxin, Lanoxin, etc.).

Sodium is regulated by the kidneys and adrenal glands. Many conditions can cause high or low sodium levels. The most common causes of low sodium levels include: diuretic usage, other medications, and excessive water intake by patients with heart or liver disease. Carbon dioxide reflects the acidity of the blood. Uncontrolled diabetes, kidney disease, metabolic disorders, and chronic hyperventilation can cause low carbon dioxide levels.·

Mononucleosis (Mono) Test:

Physicians use mono tests to detect the presence of the virus that causes mono. Mono usually involves a sore throat, swollen lymph nodes, fever, and fatigue. The Epstein-Barr virus causes mono. It spreads from person to person through saliva. Most people have mono during childhood. It often stays quiet in the body long after the symptoms go away and can become reactivated later in life. Reactivation usually occurs when disease, cancer treatment, or an organ or bone marrow transplant has weakened the immune system.

Pregnancy Test:

Definitive pregnancy testing involves determining the presence of human chorionic gonadotropin (HCG), a placental hormone, in the blood or urine. A pregnancy test shows positive results when the HCG level reaches at least 25 mIU. HCG typically does not reach this level until 4 to 6 weeks after the first day of the last menstrual period. Therefore, doctors advise that a woman waits until at least 2 weeks after missing a period to take a pregnancy test. Waiting reduces the number of false negatives thereby reducing the cost of testing. HCG tests have a 97-98% reliability rate. This rate is similar to that of home pregnancy tests.

Protime:

A "protime," or prothrombin time, gauges liver function by measuring how well a person's blood clots. The liver makes proteins called clotting factors that help blood to coagulate. If the liver is failing then it stops making enough of these factors and the protime becomes prolonged. A normal protime is usually about 11-14 seconds. A protime is considered prolonged if it is more than 1.2 times the control time (16.8 seconds). The test involves pricking the patient's finger to draw blood. The blood is applied to a test strip and a small electronic device analyzes the blood sample. The machine determines whether the blood is in the appropriate clotting range.

This test varies from one lab to another and has essentially been improved by using the International Normalized Ratio (INR). The INR is calculated from the protime (PT) by dividing by a standard reference value. This modified PT allows the INR to be accurately compared from one lab to another which can be very important for individuals treated with anticoagulants. Most physicians use the INR to follow people treated with Coumadin (warfarin). The normal INR for a person not on medications is 1. The most common goal range for treatment with coumadin is 2.0 - 3.0, although there are many exceptions.

Strep Throat Test:

Strep throat is caused by the Group A Streptococcus bacteria. A strep throat screen involves swabbing the back of the throat with a sterile cotton swab. The doctor takes care not to touch the inside of the mouth, tongue, or teeth while swabbing the throat to avoid contaminating the specimen. He/she then places the swab in a test tube, adds a reagent to extract the bacteria and then tests the extraction for Group A streptococcus. Strep screening is not always accurate. If the screen shows positive results then it is extremely likely that the patient has strep. If the test turns out negative, the technician performs a throat culture to verify that there is no strep bacteria present.

A throat culture is similar to the screening in that the doctor swabs the back of the patient's throat for a sample. Instead of extracting the bacteria into a test tube, etc., he/she places the swab on a blood agar plate containing special nutrients. These nutrients isolate and promote the growth of the strep bacteria if it exists in the specimen. If present, it is almost always detected within 24-48 hours after "plating" the swab.

Strep throat is treated with antibiotics to prevent complications. People being treated with antibiotics are no longer contagious by 24 hours after treatment begins and if fever is gone can return to school or work.

Thyroid Stimulating Hormone (TSH):

TSH is a hormone secreted by the anterior pituitary gland in the brain. TSH stimulates the thyroid to produce more hormones (T4 and T3). Thyroid hormones control the body's metabolism. When the thyroid produces too few hormones, hypothyroidism occurs. Hypothyroidism is an overall slowing down of bodily functions. It can cause fatigue, sensitivity to cold, and weight gain. When the thyroid produces too many thyroid hormones, hyperthyroidism occurs. Hyperthyroidism can cause rapid heartbeat, weight loss, and dizziness. Both conditions appear quite frequently in women older than 50. Consequently, doctors suggest that women age 65 and older get tested every three to five years. Individuals of any age should be checked if they develop the above symptoms and fail to improve with time.

The TSH test determines whether the thyroid produces the correct amount of hormones. The test involves a quick blood sample, usually taken from a patient's forearm. Laboratory technicians test the blood to determine the hormone levels. If a patient's levels fall outside of the normal range (the normal range varies between medical centers as different centers use different instruments to make the measurements) he/she may have a thyroid disorder.

Urinalysis:

An average adult produces about 1.5 liters (3 pints) of urine each day. The body needs to excrete about 0.5 liter (1 pint) of urine daily to get rid of its waste products. Excessive or inadequate production of urine may indicate illness. Doctors often use the urinalysis (the physical, chemical, and microbiological analysis of urine) to help diagnose disease, monitor treatment, and detect the presence of a specific substance in a patient's urine. For instance, the presence of glucose, represents a sign of diabetes mellitus; bacteria in the urine signals an infection of the urinary system; and red blood cells in the urine may indicate cancer of the urinary tract.

Normal test results for urine include: a color that varies from colorless to dark yellow; a specific gravity between 1.006 and 1.030 - the higher the number, the more concentrated the urine; and a pH, or relative acidity between 4.6 to 8.0 - the average is 6.0.Normal urine tests DO NOT contain sugars, ketones, proteins, red blood cells, hemoglobin, bilirubin, or white blood cells. High levels of sugar and ketones in the urine may indicate diabetes. Protein in the urine may indicate kidney disorders. Blood in the urine may indicate bleeding from the kidney, a urinary tract infection, or trauma from rigorous exercise. Bilirubin in the urine may indicate liver or bile duct disease. Nitrites and white blood cells may indicate a urinary tract infection.

Vitamin B12:

Vitamin B12 is a B-Complex vitamin and serves many important functions in the body. It maintains the myelin sheath that surrounds the nerves, aids in the production of red blood cells, helps the metabolism of fatty acids, carbohydrates and proteins, and is essential for growth in children. Medical experts also believe that Vitamin B12 boosts energy levels. Eggs, milk, cheese, liver, and beef contain Vitamin B12. Vegetables do not. Consequently, doctors encourage vegetarians to take Vitamin B12 supplements. Heavy drinkers, smokers, pregnant women, the elderly, and people taking ulcer medications are also encouraged to take supplements. Recommended dosages range between 5 mcg and 50 mcg.

A deficiency in Vitamin B12 can produce anemia, menstrual problems, mental difficulties, tiredness, and trembling.