Glossary of Lab Tests

I have tried to explain the common "routine" lab tests. The letter, which accompanies the lab report, explains the tests of concern to me, since a test can fall outside the "normal range" and be of no clinical significance to you. The letter hopefully has enough explanation that you understand your condition. If not, call or email your questions!

1. CBC (complete blood count) measures the number of red and white blood cells. Hemoglobin and hematocrit measure for the presence of anemia, and the opposite, excess red cells. White blood cell count and differential gives information about the presence of infection and disorders such as drug reactions, and leukemia.
2. Chemistries
   1. Kidney function - BUN and creatinine give us an idea of how well your kidneys are working. High levels of BUN and creatinine reveal impaired kidney function. Electrolytes measure the composition on the water phase of your blood- sodium, potassium, chloride and bicarbonate are the four usually referred to as "electrolytes", though there are many electrolytes. Changes in levels of sodium, potassium, and bicarbonate are often caused by kidney disease, or use of diuretics, so monitoring is necessary if you take diuretics.
   2. Liver tests - The common measures of liver function include SGOT (AST), SGPT (ALT), bilirubin, alkaline phosphatase, although there although there are many others, ordered for specific liver problems. The pattern of elevations suggests what type of liver problem you might have, though mild elevations often have no particular significance.
   3. Diabetes - blood glucose (sugar) is measured either at random, where normal range is up to 140, or fasting, where glucose should not exceed 110. The glycohemoglobin, or hemoglobin A1C, is a measure of diabetes control over a longer time. The A1C changes according to long-term control of diabetes, say, weeks, whereas the diabetic can have a poor degree of control, but normal glucose for the moment. The goal of diabetes therapy is to lower the A1C into the 6-7 range.
   4. Gout - uric acid is the test associated with gout. Although the normal range is up to 6.8, the higher the level, generally the more likely acute small joint pain is coming from gout.
   5. Urine tests - the urinalysis includes several important item- the presence of glucose, protein, or various types of cells and bacteria, give clues to the cause of symptoms and signs of infection, nephritis, complications of diabetes.
   6. Cholesterol profile - there are several components to the cholesterol profile, and each one has individual meaning, while there are combinations or patterns, which are also important.
      1. Total cholesterol- accepted levels are below 200, and 130- 200 is usually good.
      2. LDL ("bad") cholesterol- LDL is consistent in its relationship to coronary disease. Levels above 130 should be treated with medication, usually statins, if diet does not do the job. Goals of therapy are to lower the LDL below 100, maybe as low as 80.
      3. HDL ("good") cholesterol- Generally, the higher, the better, starting at 45.
      4. Triglyceride- The one component of the profile, which is accurate only if drawn after an overnight fast, with alcohol, withheld for 24 hours. Triglyceride elevations, greater than 175, usually coincide with low HDL, in patients with "metabolic syndrome"- abdominal girth obesity, hypertension, and perhaps adult onset diabetes.
      5. Ratios- it is of some help to look at the cholesterol/HDL ratio. A correlation of this ratio to heart disease can be drawn. A low ratio simply means that a high percentage of cholesterol is HDL, and that's good!
   7. Thyroid tests - The TSH measures the pituitary hormone, which controls the thyroid. High levels mean the thyroid is failing, and low levels suggest the thyroid is overactive. The T4, and Free T4 actually measure the levels of circulating thyroid hormone. High levels diagnose an overactive thyroid; low levels represent underactive thyroid function.