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November 2003

A Comprehensive Guide to Preventative Blood Testing
By Penny Baron

Chemistry and complete blood count(CBC) PANEL
The chemistry panel provides a wide range of information to assess cardiovascular, endocrine (glucose levels), hepato-biliary, and kidney function. The CBC panel provides information on the presence of infectious organisms, anemias, nutritional deficiencies, lymphoproliferative disorders (i.e., leukemia), and other hematological disorders.

Chemistry cardiovascular system tests include total cholesterol, HDL- and LDL-cholesterol, triglycerides, and the ratio between total cholesterol and HDL levels, which is more valuable as a predictor of heart disease than total cholesterol or HDL levels alone. When assessed along with C-reactive protein and homocysteine blood levels, the information attained offers a very powerful indicator of cardiovascular status, including risk of future heart disease.

The chemistry panel also looks at fasting glucose levels in the plasma. Skewed values may indicate problems with glucose metabolism, such as hyperglycemia (diabetes mellitus) or hypoglycemia (low blood sugar, which may preempt hyperglycemia in some individuals), acidosis or ketoacidosis, and further problems with carbohydrate metabolism.

Abnormal levels of protein/albumin/globulin, albumin/globulin ratio, bilirubin, alkaline phosphatase, lactic dehydrogenase (LDH), AST (SGOT), ALT (SGPT), iron, cholesterol, and cholesterol lipoproteins are indications of potential liver/biliary problems. These may include liver damage induced by alcohol or drug use, liver cancer, or obstruction of the bile duct, among others. Together, ALT and AST allow for differential diagnosis of disorders associated with the hepato-biliary system and the pancreas. High levels of alkaline phosphatase may also indicate abnormally high levels of vitamin D.

Kidney function may be assessed by evaluating blood levels of the following: blood urea nitrogen (BUN), uric acid, creatinine, BUN/creatinine ratio, sodium, potassium, and chloride ions. BUN measures the amount of urea nitrogen (a breakdown product of protein metabolism) in the blood. Most diseases involving the renal system affect urea excretion by the kidneys and will elevate BUN levels. Creatinine, a breakdown product of creatine metabolism (creatine is an important constituent of muscle), is excreted by the kidneys—abnormal levels may indicate renal failure or dehydration (elevated levels) or myasthenia gravis or late-stage muscular dystrophy (decreased levels). The ratio between BUN and creatinine may help determine the reason behind decreased kidney function (such as dehydration). Sodium, potassium, and chloride ion levels assist in the evaluation of hydration status and electrolyte balance. Low levels of potassium may indicate acute renal failure.

Hematological abnormalities and infection
Complete blood counts include red blood cells (RBCs) and white blood cells (WBCs) and their components: hematocrit, hemoglobin levels, and platelet counts.

RBC, hematocrit, and hemoglobin
Abnormally low RBC levels may indicate iron, folate, and vitamin B6 and B12 deficiencies. Low hemoglobin or hematocrit levels may indicate anemia; high hematocrit values may suggest dehydration. Abnormal distribution of the RBC width (RDW) compared with the mean corpuscular hemoglobin volume (hematocrit divided by RBC count) may detect such problems as aplastic anemia, thalassemia, anemias, and deficiencies of iron, folate, and vitamin B12.

Platelets are an essential part of the coagulation (clotting) cascade and normal levels are necessary to maintain hemostasis. Decreased platelet counts may be seen in patients undergoing chemotherapy, and in hemolytic anemia, leukemia, and other disorders that diminish clotting ability.

WBCs and their components (lymphocytes, monocytes, neutrophils, eosinophils, and basophils)
Increased levels of all types of WBCs in the blood are usually associated with bacterial, viral, parasitic, or protozoal infections. Neutrophils, which are the first WBCs to respond to infection, often indicate infection or emotional stress (increased levels) or chronic infection, bone marrow depression, or iron, folic acid, or vitamin B12 and B6 anemias (decreased levels). Differential assessment of the CD4/CD8 T-lymphocyte ratio (a separate test) may confer important information concerning immune status, especially in patients who are immune-suppressed (i.e., HIV/ AIDS). The presence of eosinophils in the blood is a good indication of parasitic or fungal infection, or a response to allergy. The number of monocytes in the blood is often increased (very high levels) in patients with leukemias and Hodgkin’s or non-Hodgkin’s lymphoma.

Total and Free Testosterone
Free testosterone is included in both the male and female panels.

Testosterone is produced in the testes in men, in the ovaries in women, and in the adrenal glands of both men and women. In men, testosterone production is stimulated by luteinizing (LH), which is produced by the pituitary gland and by Leydig cells in the testes. Testosterone levels normally decline with age, dropping to approximately 65% of young adult levels by age 75. This drop in testosterone is partially responsible for the significant physiologic changes seen in aging men.

Less than 2% of testosterone is typically found in the “free” (uncomplexed) state in the serum of both men and women. Approximately 50% is bound to sex hormone-binding globulin (SHBG) and the remainder to albumin. In men, free testosterone (an androgen, or “male hormone”) levels may be used to evaluate impotence or infertility. In women, high levels of free testosterone may indicate hirsutism (excessive hair growth, especially on the face and chest), which is often indicative of polycystic ovaries and, less commonly, ovarian cancer. Increased testosterone in women also suggests low estrogen levels.

Total testosterone (complexed and uncomplexed) is useful for assisting with differential diagnosis in males (LH secretion and Leydig cell function, gonaldal and adrenal function, diagnosis of hypogonadism, hypopituitarism, Klinefelter syndrome, and impotence) and in females (Stein-Leventhal syndrome, masculinizing tumors of the ovary, tumors of the adrenal cortices, and congenital adrenal hyperplasia).

DHEA-S (dehydroepiandrosterone sulfate)
DHEA, often used as a muscle-building supplement by bodybuilders, measures adrenal cortical function. Elevated levels of this hormone, which peaks during one’s 20s, may be indicative of CAH (congenital adrenal hyperplasia), a group of disorders that result from the impaired ability of the adrenal glands to produce corticosteroids. DHEA is also being evaluated in clinical trials for its role in memory and Alzheimer’s disease, though results are as yet inconclusive.