This article written by Dr. Christopher Beyrer for the "Baltimore Alternative" is reprinted with permission, and has been updated by AIDS Action Baltimore President, Lynda Dee.

When physicians want to know how a patient is doing clinically they often ask "what are the numbers?"  These "numbers" are lab results, usually from tests done on blood.  For people with AIDS and their caregivers the "numbers" are quite important and are often used in deciding key issues of care.  Of course, lab results are no substitute for a complete evaluation, and no one lab test is ever an answer, yet we know enough about AIDS now to tell a good deal from these tests.  The lab tests used to examine PWAs are not difficult to understand, but they're often explained in medical jargon, a language closer to old church Latin than to plain English or Spanish.  Here, then, is an explanation of what some of "the numbers" mean.

The first test many of us encounter is the HIV test.  This is sometimes mistakenly called the "AIDS Test" but it's nothing of the kind.   AIDS is a syndrome, which means it is diagnosed on the overall picture of the patient.  There is no one test for AIDS.  The HIV test looks for antibodies to the HIV virus.  Antibodies are proteins in the body makes in response to an infection or to an exposure, or to a vaccine.  So the HIV test tells us if a person has been exposed and made antibodies to the virus.  It can take the body up to four months to make these antibodies after exposure to HIV, so a negative test can still occur when the virus has been in the body only a short time.

The most important indicator of HIV activity and risk of progression to AIDS is a person's viral load.  "Viral load," "viral burden," "HIV burden," "HIV load," and "HIV RNA" all refer to the same thing; i.e., the actual amount of HIV in your bloodstream.  Viral load testing measures the amount of HIV in your blood plasma.  HIV viral load testing detects minute amounts of HIV ribonucleic acid (HIV RNA), which is the genetic material of HIV.   Viral load test results are usually expressed as the number of HIV RNA copies per milliliter (copies/mL) of blood plasma.  Depending on the sensitivity of the assay used, test results may range from fewer than 25 copies/mL to several million copies/mL.

Another important test is the CBC, the Complete Blood Count.  The CBC counts the cells in the blood, the red cells, white cells and platelets (blood is made up of these various cells and the clear fluid plasma - the plasma is examined by blood chemistries).  The majority of cells are red cells, the cells that carry oxygen.   There are too many to count, so the percentage (%) of whole blood which is red cells is used.  Typically the blood is 38 - 54% red cells in men and about 36 - 47% red cells in women.  This percentage is called the Hematocrit.  A low Hematocrit is seen in anemia, a common problem in PWAs and a common complication of therapy with AZT.   Hemoglobin (Hgb), is the iron containing protein in red cells, it's measured along with the hematocrit to evaluate red cells.

After the red cells we look at the white cells, the cells involved in immunity.  The total number of white cells is measured by the White Blood Count or WBC, and is normally between 5,000-9,000 (doctors often drop these zeros and say the WBCs are 5 or 9).  A low WBC is often a sign of low immune resistance.  In healthy people a high WBC is a sign of an acute infection.  Very low WBCs (below 3,000) are often seen in AIDS and can be a complication of numerous drugs including antiviral drugs like Gancyclovir.

The white cells are actually a family of cells which includes, among others, the lymphocytes.  Lymphocyte means simply the lymph cells, and these are also the cells in lymph nodes.  Lymphocytes again are a family (or cell line) an are of central importance in AIDS (the "L" in HTLV-III, an older name for HIV was for lymphocytes).  Two key members of this family of cells are the T-helpers and T-suppressors, the "T" here stands for Thymus, the immune gland in the neck where these cells develop.  The names get hairy here, but all the following mean the same thing: T4 = CD4 = T-helper.  A healthy person has about 1,100 - 1,400 T-helpers and about 700 - 900 suppressors.  This means a ratio, or proportion, of 1400 to 700 or 2 to 1.  This number is called the helper to suppressor ratio.  When the T-helpers (remember your doctor may say T4s, CD4s) fall below 400 - 500, many physicians begin combination antiviral therapy.  When T4s fall to below 200, the patient usually has signs and symptoms of severe immune deficiency and is at risk for many infections.   T4 cells below 100 make physicians nervous - and they should, at this level of immunity a PWA needs careful management to avoid infections.  So "the numbers" here are watched very closely.

The CBC also looks at the last cell type, the platelets.  Platelets are tiny cell fragments that play an essential role in blood clotting.  There are usually between 200,000 to 500,000  in a blood sample.  Low platelets are often seen in early HIV disease (especially in children) and very low platelets are sometimes seen in advanced disease - this can lead to easy bruising and easy bleeding.

There are, of course, many other kinds of tests important to PWA, and they are usually geared to each person's particular problem.  The ones described should be given to every PWA.