Being Alive 1994 Mar 5: 9
Complete Blood Count (CBC)
Perhaps the most routine test is the complete blood count (CBC). The
CBC examines formed elements (red blood cells, white blood cells,
platelets), and plasma (which is made of water, protein and other
substances). HIV+ people with no symptoms should have a CBC every six
to twelve months. Those with symptoms should have a CBC every three to
six months but those on AZT (particularly within the first four to six
months) should have it done every few weeks.
White blood cells (WBC). White blood cells or leukocytes defend the
body against infection. The total number of white blood cells ranges
from 4,000 to 11,000 per cubic millimeter in the average healthy
adult. A high WBC count may mean the body is fighting an infection. A
low WBC count may mean there is a bone marrow problem either from
chronic disease or from drugs like AZT or ganciclovir. Tuberculosis,
histoplasmosis, and other fungal diseases may also cause bone marrow
problems such as "cytopenia" or low cell counts.
Red blood cells (RBC). These cells carry oxygen throughout the body.
The number of RBCs within the normal range varies from 3.6 to 6.1
million per cubic millimeter. Too many RBCs (or platelets) in the
bloodstream may cause slow blood flow and compromise circulation. A
low RBC may signify anemia, a shortage of red blood cells, or
hemoglobin; this usually reflects underproduction or premature
destruction of the cells.
Hemoglobin is a protein that enables RBCs to carry oxygen from the
lungs to the rest of the body. The amount of hemoglobin determines how
much oxygen the RBCs are capable of carrying to other cells. Normal
hemoglobin levels range from 12 to 16 grams per deciliter for women
and 13.5 to 18 for men. These levels are often low, among HIV+ people,
even those not on medications. Epogen is an injectable drug that
stimulates the production of red cells. It is used in anemic AIDS
patients to reduce the frequency of transfusions.
Hematocrit is the volume of RBCs expressed as a percentage of the
total blood volume. If you spin a sample of blood so that the cells
settle to the bottom of the tube, the percentage of volume occupied by
the cells alone is called the "hematocrit." The hematocrit shows the
oxygen-carrying capacity of the blood. This value also tells whether
the blood is too thick or too thin. The average range is 40%-54%.
Mean corpuscular volume (MCV) is the average volume of the individual
red blood cells. MCV is calculated by dividing the hematocrit by the
total RBCs. The average range is 81-101 femoliters. A low MCV
indicates the cells are smaller than normal. This most commonly occurs
because of an iron deficiency or chronic disease. AZT may cause the
MCV to rise above normal, which may also happen if there is a B12
Mean corpuscular hemoglobin (MCH) and mean corpuscular hemoglobin
concentration (MCHC) are measures of the amount and volume of
hemoglobin in the average cell. The MCH average range is 27-35
picograms. The MCH results from dividing total hemoglobin by total
RBCs. The average range from MCHC is 31-37%.
Platelets are an element of the blood that are important for blood
clotting. They are formed in the bone marrow. Too many platelets may
cause "sludging" of the blood flow. People with HIV disease may have
low platelets or "thrombocytopenia." Drug reactions may also be
responsible for the destruction of RBCs or platelets. The average
platelet count is 150-440. The chance of major bleeding rises as the
platelet count drops.
Differential is a breakdown of the different types of white blood
cells and is usually expressed as a percentage of the total WBCs.
Multiplying these percents by the total WBCs gives the "absolute"
counts. For example, if the percent of lymphocytes is 30% and the
total WBCs is 10,000, the absolute lymphocyte count is 3,000.
Segs, Neutrophils, Polys (polymorphonuclear cell) are WBCs involved in
fighting bacterial infections. Neutropenia is a drop in the absolute
neutrophil count to below 500. Neutropenia makes people with AIDS
especially susceptible to bacterial infections.
Lymphocytes (lymphs) are cells that produce antibodies, regulate the
immune system, and fight viruses and tumors. The T4 or CD4 cell is
part of this lymphocyte family, but is not included as part of a
routine CBC. Ranges vary from 10-45%.
Monocytes or Macrophages (Monos) are WBCs involved in fighting
Eosinophils (Eos) are WBCs usually involved in allergic-type
reactions. An elevated eosinophil percentage can help in diagnosing
certain types of allergic diseases. Ranges vary from 0-8%.
If all three major blood counts (RBC, WBC and platelets) are
unexplainably low, particularly in advanced stages of HIV infection,
one might consider the possibility of an opportunistic infection
(especially MAC or CMV) as well as underlying HIV infection
suppressing the bone marrow, or malignancies such as lymphoma.
Chemistry (Chem) Panel
A large part of your laboratory report examines chemicals in your
blood and identifies whether body processes are working correctly.
Typically, 24 of these values are included in a "Chem 24 report," also
known as a SMAC or SMA20. Your physician or clinical nurse manager may
be able to help you decipher your lab values. Chemistry panels should
be administered once a year if you're not taking medication, more
often if you are.
Here are some of the more important values for people with HIV
Glucose is sugar in the blood, most commonly used to monitor diabetes
mellitus. Glucose levels may become abnormally high or low when
pentamidine is given intravenously.
Sodium, Potassium, and Chloride are also known as electrolytes. These
must be monitored carefully in dehydration, kidney disease, and during
intravenous therapy (especially with foscarnet). Sodium levels reflect
salt/water balance. Potassium levels rise in kidney failure, and may
be low after severe vomiting or diarrhea.
BUN stands for blood urea nitrogen. This tends to rise in dehydration
and in kidney or heart failure. Prednisone and other steroids may
cause BUN to rise.
Albumin is one of the two major types of protein in the blood.
Manufactured in the liver, albumin decreases in chronic liver disease.
It also reflects one's general nutritional status.
Globulins are a mixture of proteins that include immunoglobulins, or
antibodies. Globulins tend to rise in asymptomatic HIV+ people.
A-G Ratio is the ratio of albumin to globulin.
Bilirubin derives from the hemoglobin of dead RBCs. Bilirubin is
excreted by the liver as part of the bile. Bilirubin causes the yellow
color of the skin and eyes (jaundice) which occurs in hepatitis, bile
duct obstruction, and other liver disorders.
Gamma GT, SGOT, SGPT, and LDH are liver enzymes. Elevation of these
tests is most common in liver disease, but may also rise from
injuries, tumors and drug reactions. People with Pneumocystis
pneumonia tend to have a more serious prognosis if they have elevated
Iron is an essential component of hemoglobin. The iron screen is
useful in identifying iron deficiency, which causes anemia (low red
blood cells and hemoglobin). Iron loss may be due to chronic bleeding,
for instance, when Kaposi's sarcoma affects the intestines.
Cholesterol and Triglycerides are fatty substances found in the blood.
They are measured to assess risk for coronary heart disease and to
follow the effect of dietary manipulations. Medication is sometimes
used to lower cholesterol if diet doesn't work alone. Triglyceride
levels tend to be elevated in later stages of HIV disease, and this
may be due to elevated levels of TNF (tumor necrosis factor).
Markers for HIV Progression
Many markers measure the presence or absence of HIV in the human
blood. HIV surrogate markers are measurements that effect HIV
activity; they are "surrogate" because they do not measure the
absolute amount of HIV. Instead they measure secondary effects of HIV
on the body. Healthcare providers often use surrogate markers to
decide on drug therapies and to monitor the effects of experimental
treatments. Virologic markers, such as p24 antigen, are used to
directly measure the presence of HIV in the human body.
CD4 Count the most commonly used marker to determine HIV progression
is also known as the CD4 lymphocyte count or T4 cell count. HIV
attacks CD4 cells which help fight infections. T-lymphocytes include
other CD4 (helper) cells and CD8 (suppressor) cells.
A significant drop in the CD4 count reflects the amount of damage in
the immune system. CD4 levels can be reported in the following ways:
- Absolute number of CD4 cells per cubic millimeter (mm3).
- Percent of CD4 cells compared to all lymphocyte cells.
- Ratio of CD4 cells to CD8 (or T8) cells.
HIV+ people should have their CD4 counts taken every three to six
months, and sometimes more often if they are taking medication or if
their CD4 count falls below 250. The normal range for an adult male is
800-1500 CD4 cells.
CD4 Percentage a comparison of the number of CD4 cells to the total
lymphocyte count (B- and T-lymphocytes). The CD4 percentage may be a
more accurate measure of HIV disease progression than the CD4 count,
because immune suppression may be present despite a high CD4 count. A
CD4 percentage below 20% suggests serious immune deficiency, even if
the CD4 count is high.
Beta 2 Microglobulin (B2M) a protein that may become elevated in HIV+
people because of lymphocyte activity. Levels can be checked in the
blood and urine. B2M may not be a good marker of HIV progression among
intravenous drug users because B2M levels do not seem to correlate
with disease progression among IDUs.
B2M results tend to fluctuate much less than CD4 counts. B2M levels
above 5.0 milligrams per liter may indicate an increased chance of HIV
Neopterin a protein secreted by macrophages, white blood cells that
act as reservoirs for HIV. Neopterin levels rise as HIV disease
progresses. Monitoring both B2M and neopterin levels may be redundant
because studies show that each is about equally capable of predicting
disease progression. Normally, neopterin levels are below 2.0
nanograms per milliliter. Levels above 15.0 nanograms per milliliter
indicate disease progression.
p24 antigen one of the proteins that make up HIV. An antigen is
anything that the immune system identifies as foreign. A positive p24
antigen test suggests active HIV replication. Someone who tests
positive to a p24 antigen test, even with CD4 counts above 500, may be
advised to start antiretroviral therapy. Levels are usually highest
both early and late in the course of HIV disease. This test is
sometimes used to monitor the progress of HIV disease and the body's
response to antiviral drugs.
p24 antibody an antibody produced by the immune system in response to
p24 antigen. Low levels of p24 antibodies are associated with HIV
disease progression. A low p24 antibody level with high neopterin
level and thrush is a sign of rapid HIV disease progression. p24
antibody levels are less standardized than the p24 antigen levels.
In the procedure known as Passive Hyperimmune Therapy (PHT), p24
antibodies from healthy asymptomatic people are infused into people
with later stage HIV disease.