Laboratory Tests Defined

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PCRI Insights May, 2005 vol. 8, no. 2
By Mark C. Scholz, MD, Director, Prostate Oncology Specialists, Marina del Rey, CA

An important first step in the screening procedure is, of course, the physical examination taken at the first visit of a patient to our practice and scheduled to be repeated each year thereafter. In addition to the tactile examination, a complete physical will include a number of blood tests which, when analyzed, can provide an early indication of disease or incipient disease.

The results of the laboratory results are written in a shorthand code that your physician can readily interpret, but that might just bewilder you as a patient. For each blood test result, the report includes (1) an entry in a column for your quantitative results and (2) an entry in a column presenting the reference range for males. In addition, if one of your results is outside of this range, that result is flagged so you can quickly see anomalous results.

But what are these tests? What do they measure? What is the possible significance of an anomalous result? The following will answer these questions for you.

The GLU test measures blood glucose levels that vary before and after meals. Patients with diabetes have blood sugar levels that remain persistently elevated. Low levels of glucose occur in patients on macrobiotic diets and are desirable in prostate cancer patients because less sugar is available to the growing tumor cells. Low levels of glucose in diabetic patients can be indicative of excess medication or insulin. Since blood glucose varies, a better way to diagnose diabetes is the glycohemoglobin blood test. An abnormal GLU result may cause your doctor to prescribe this additional blood test.

Elevation of Blood Urea Nitrogen (BUN) can result from dehydration or from a high protein diet but it can also be a result of a kidney malfunction (but when this is the case there is almost always simultaneous elevation of the creatinine level as well). BUN is very sensitive, and a modest elevation of BUN does not necessarily indicate a need for intervention. Low BUN levels have no implications of consequence.

Creatinine (CREAT) is a fairly accurate indication of kidney efficiency. Elevated levels of creatinine are indicative of kidney impairment. The development of creatinine elevation above previous baseline signals the need for further tests. Minor elevation of creatinine can be seen from aging and is usually not significant if the minor elevation remains stable. Low creatinine levels have no implications of consequence.

The concentration of Sodium (Na) in the blood is regulated by the kidneys and adrenal glands. Drinking too much water can cause abnormally low amounts in the blood, but so does heart failure or kidney malfunction. Hence, levels of sodium outside the normal range represent a significant problem that needs evaluation and correction.

Small amounts of Potassium (K) can be measured in the blood. Blood levels outside the normal range are of critical significance. Low blood levels of potassium result from diuretics (water pills) when there is an inadequate amount of potassium replacement. High blood levels can result from kidney disease or from excess potassium replacement. Occasionally, potassium can be elevated in the breakdown process of the red blood cells (hemolysis), which occurs when the blood is being drawn. When hemolysis is suspected, the blood draw is repeated to determine if the potassium elevation is artifactual. Levels of potassium outside the normal range represent a significant problem that needs evaluation and correction.

Abnormal Chloride (CL) levels usually accompany abnormalities of sodium or potassium. Borderline low or high levels of chloride generally have no significance.

Calcium (Ca) blood levels are tightly regulated by parathyroid hormone and vitamin D. Over-active parathyroid glands can also cause excess blood levels of calcium. Grossly elevated calcium levels are dangerous and can cause sleepiness and heart arrhythmias. Low levels of calcium can cause muscle spasms, typically in the hands. Low levels of calcium can also be observed in patients with low albumin levels (protein levels) in the blood. Elevated levels of calcium can occur by taking excess amounts of vitamin D. The accuracy of the blood calcium can be confirmed with a more accurate test called ionized calcium.

HEPATIC PANEL (Liver function tests)
Transaminases (AST/ALT) are the most sensitive indicators of liver cell irritation or damage. AST and ALT (also known as SGOT and SGPT) can occasionally elevate to minor degrees from viral infections or from excess alcohol. Larger degrees of elevation can occur as a result of toxicity from medications or from cancer spread. AST/ALT elevation can also occur after a heart attack. Low levels of AST/ALT are of no significance.

Blood bilirubin (TBIL) levels are reflective of the rate that the body recycles the red cells in the blood; bilirubin is a breakdown product of old, used up red cells. Elevations of bilirubin can occur with bile duct blockage if the red cell breakdown process is accelerated by disease. A mild chronic elevation of bilirubin may be a benign genetic condition that does not cause illness. (DBIL) is a sub fraction of bilirubin. Relative changes of the two forms can help distinguish the different causes of bilirubin elevation.

Alkaline Phosphatase (ALP) is another indicator of liver health and function. ALP is also a produced in the bones so elevations of ALP can occur either from problems originating from the liver or bone or both. Liver cell function problems can cause an elevation of ALP in a manner similar to AST/ALT. ALP is also sensitive to blockage of the bile ducts, so elevations of ALP in conjunction with elevations of Bilirubin indicate bile duct blockage. Low ALP levels are not of concern.

Total Protein (TP) is a simple measure of the amount of protein in the blood including albumin. The non-albumin portion of the blood includes antibodies, that function as a portion of the immune system. Elevated levels of TP can be seen in immune derangements where antibodies are over-produced. Albumin is the most common protein circulating in the blood. Albumin fulfills a number of functions such as maintaining vascular blood volume, binding hormones, and acting as a storage reserve for protein. Low albumin levels are reflective of malnutrition, liver disease, or kidney disease. Elevation of albumin levels is usually minor and of no consequence.

The CBC contains several different measures of importance though for PC patients the real issue is the presence or absence of anemia. Anemia is the relative reduction of red cells in the blood resulting in a decrease in oxygen carrying capacity. Severe anemia can be felt as tiredness and shortness of breath. Anemia is measured by three factors in the CBC: Hematocrit (HCT), Hemoglobin (HGB), and Red Blood Count (RBC). An HCT level less than 40 in men constitutes a low level. Symptoms of tiredness and shortness of breath do not usually occur until the HCT declines to around 32 though there are occasional exceptions. A low HCT is treatable with a non-toxic substance called Erythropoietin.

The other important measures in the CBC take on more significance in patients receiving chemotherapy. Chemotherapy can cause reductions in Platelet count (PLT) and White blood count (WBC). Platelets help the blood clot normally. White blood cells are part of the immune system. The WBC is broken down into Granulocytes (GRAN) and Lymphocytes (LYM). An elevated level of granulocytes is indicative of an underlying bacterial infection. Viral infections can cause low lymphocyte counts. MCV, MCH, and MCHC are measures of red cell dimensions. MCV is the most commonly utilized. Low MCV can be seen in iron deficiency and in a congenital anemia called thallassemia. High MCV can be seen in liver disease and B12 deficiency. RDW is a measure of red cell size variability. Elevation of RDW can occur early in the development of iron deficiency.

Triglyceride (TRIG) is simply another name for fat. Elevated fasting triglyceride levels indicate a higher risk for coronary arteriosclerosis. However, transient declines in the White Blood Count (WBC) and the triglyceride levels are not as accurate predictors of arteriosclerosis as cholesterol.

Previously, total cholesterol (CHOL) levels of over 200 were thought to be indicative of an increased risk for arteriosclerosis. This is true but better indicators have been developed. Low Density Lipoprotein (LDL) cholesterol or “bad cholesterol” is an indicator for the risk of developing arteriosclerosis. The American Heart Association recommends that LDL cholesterol should be less than 100 to prevent deposition of cholesterol on the arterial wall. Modern statin drugs such as Lipitor® dramatically lower LDL levels in the blood and can lead to reversal of blood vessel clogging.

High Density Lipoprotein (HDL) cholesterol is called “good cholesterol” because higher levels of HDL protect against the development of arteriosclerosis by scavenging excess cholesterol from the walls of the blood vessels. The HDL level can be increased with exercise and niacin. Studies show that the higher the level of HDL the lower the risk for heart disease. Levels of HDL that are under 40 represent a particular concern.

Ultra-sensitive Thyroid Stimulating Hormone
is the hormone that stimulates thyroid hormone production. Elevated levels of TSH indicate blood levels of thyroid hormone are inadequate. Low levels of TSH indicate that the thyroid may be overactive. If patients are already taking thyroid hormone, TSH can be used to ensure that the correct amount of hormone is being administered.

C-Reactive Protein (CRP) is a protein marker for inflammation. Elevated levels are usually caused by infections and arthritic conditions. More recent studies have shown that abnormal levels are also associated with an increased risk of heart attacks and colon cancer, so CRP results are now given equal weight to CHOL results.

For more information about various tests, see:

Lab Tests Online

Life Extension Foundation