TYPES OF BLOOD TEST

Serum Electrolyte Tests

Blood contains various salts that are needed for normal function. The electrolytes can be affected by high blood pressure, diabetes mellitus, and heart failure, as well as by many of the medications used for their treatment. If you are receiving diuretics for one of these conditions, you should expect to have your electrolytes measured every few months. This is necessary to avoid side effects.

Blood Urea Nitrogen and Creatinine Tests

Blood urea nitrogen (BUN) and creatinine are normal waste products produced by the body. Under ordinary conditions they are removed from the blood by the kidneys. In a disease of the kidneys these elements accumulate, however. Kidney disease and high blood pressure are closely interrelated. It is important to have these substances measured if you suffer from high blood pressure as well. Medications used to treat heart disease, kidney disorders, and high blood pressure include diuretics and digoxin. The level of BUN and creatinine in the blood will determine their dosage. If the kidney disease becomes severe, the level of BUN and creatinine rises. During tests of kidney function, the electrolytes are often measured at the same time.

Liver Function Tests

The liver manufactures important substances from nutrients. The liver also disposes of the waste products of metabolism. Bile, produced by the liver, is necessary for the digestion of fats. Therefore, liver abnormalities can have a severe effect on the body.

Liver tests also examine enzymes, which are contained within liver cells. These leak into or accumulate in the blood when the organ is damaged or diseased. An excess amount of bilirubin in the blood may indicate a blockage of the biliary ducts, which allow bile to flow from the liver to the small intestine. When this accumulates, a yellow discoloration of the skin (jaundice) usually occurs.

The severity of liver diseases varies, so it is often necessary for function tests to be taken frequently during a liver illness. As the disease subsides, your physician may continue to measure these substances to ensure that the liver has returned to normal. In some disorders, the symptoms may be very mild. Sometimes the only abnormality that may confirm that an illness is present is a mild irregularity in liver function tests, so these would be done periodically to judge whether the disease is progressing or resolving.

Uric Acid Tests

Uric acid is a normal constituent of the blood. If it accumulates, it can cause kidney damage or gout, a painful condition of the joints. People who suffer from gout usually have raised amounts of uric acid in their blood. Kidney disease and diuretics used to treat high blood pressure and heart failure can increase the level of uric acid in the blood.

If you suffer from gout or have a raised uric acid level as a result of kidney disease or the use of medications, your blood should be checked periodically. This is important because medications can lower the amount of uric acid. Periodic blood tests confirm that the drugs are working.

Calcium and Phosphorus Tests

Calcium and phosphorus are usually measured together because they interact with each other very closely. They are affected by diseases of the bones and kidneys and when the parathyroid glands are abnormal. Certain medications also affect their blood levels. The tests may be repeated if you suffer from an illness that alters their normal values.

Thyroid Function Tests

Disease of the thyroid gland is quite common in older individuals, but the diagnosis is less easily made than in younger people. Physicians often order thyroid function tests to look for evidence of excessive or decreased working of the gland. If you have thyroid disease and have been treated for it or are presently taking thyroid medications, you can expect to have your thyroid function measured periodically.

Hormone Tests

In addition to thyroid, hormones produced by other endocrine glands can be measured to determine whether these glands are working normally. When the body produces an excess or too little of an individual hormone an illness ensues. Measurement of the amount of hormone in the blood can help diagnose these disorders and evaluate treatment.

Blood Sugar Tests

Abnormalities of blood sugar levels occur in diabetes mellitus, so it is important that your blood sugar be tested to diagnose the disorder and to follow its control once treatment has started. If you are suspected of having diabetes mellitus, it may be sufficient to have an isolated sample of blood sugar measured. If this is excessively high, a definite diagnosis sometimes can be made. Often it is better to have the level of blood sugar estimated while you are in a fasting state (without breakfast). At other times, a measurement done two hours after a meal is more useful.

If diabetes mellitus cannot be diagnosed from a fasting sugar sample or one taken two hours after a meal, your physician may request a glucose tolerance test, in which you drink a measured amount of liquid sugar. An estimation of your blood sugar level is done before you drink the liquid and tests are repeated for the next few hours. This determines whether the amount of blood sugar is excessively high.

If you are being treated for diabetes mellitus, you must have your sugar levels measured periodically. The blood may be taken when you are in a fasting state, or after a meal, or in the afternoon, depending on whether you are taking pills, insulin, or merely following a diabetic diet. Some people utilize home-monitoring kits to measure blood sugar levels. This allows frequent monitoring without having to visit the doctor’s office or a laboratory. This testing must be done in conjunction with your doctor.

Erythrocyte Sedimentation Rate Tests

The erythrocyte sedimentation rate (ESR) test has been available for many years, and even though we still do not completely understand how it works, it is very useful. The sedimentation rate becomes elevated when the body is suffering from an inflammatory illness. The test’s main use is in arthritic diseases, but it is also used in some blood disorders. It may also be helpful in alerting the physician to an arthritic, inflammatory, or blood disorder and in assessing the results of treatment. Therefore, the ESR may be measured frequently if you are being treated for an inflammatory or arthritic condition.

Arthritis Tests

In addition to the sedimentation rate, special tests can be used to diagnose various types of arthritis. For instance, rheumatoid arthritis may be characterized by the rheumatoid factor, an abnormal antibody found in the blood of people with this disorder. With treatment, the level of this substance in the blood may decrease, confirming that the therapy is effective. There are many other types of tests for arthritic disorders. Depending on the particular type of arthritic problem, your physician will request the appropriate test.

Cholesterol and Triglyceride Measurements

Cholesterol and triglycerides are important fats found in the blood. These fats are carried by special proteins known as

HDL (high density lipoproteins) and LDL (low density lipoproteins). We know that the amounts of these blood components in individuals may reflect their risk for certain diseases such as atherosclerosis and heart attack. What is not known is whether the risk from elevations of these blood fats continues into your later years.

Your physician may decide to measure your blood cholesterol, triglycerides, and HDL and LDL concentrations to learn whether you are at special risk from elevated levels. Depending on the results of the tests, your age, and your medical condition, your doctor may recommend that you follow a special diet or take medications that may lower your blood fat levels.

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