How is it used?When is it ordered?What does the test result mean?Is there anything else I should know?
The CD4 count tells your doctor how strong your immune system is, how far
HIV disease has advanced (the stage of the disease), and helps predict the risk of complications and debilitating infections. The CD4 count is most useful when it is compared with the count obtained from an earlier test.
The CD4 count is used in combination with the viral load test, which measures the level of HIV in the blood, to determine the staging and outlook of the disease.
The CD4 count is also used to identify possible health problems for which you may be at risk and to determine which medications might be helpful.
A CD4 count and a
viral load test are ordered when a person is first diagnosed with
HIV as part of a baseline measurement. Both tests should be repeated about two to eight weeks after starting or changing anti-HIV therapy. If treatment is maintained, a CD4 count should be performed every three to six months thereafter.
What does the test result mean?NOTE: A standard reference range is not available for this test. Because
reference values are
dependent on many factors, including patient age, gender, sample population, and test
method, numeric test results have different meanings in different labs. Your lab report
should include the specific reference range for your test. Lab Tests Online strongly
recommends that you discuss your test results with your doctor. For more information on
reference ranges, please read Reference Ranges
and What They Mean.
Normal CD4 counts in adults range from 500 to 1,500 cells per cubic millimeter of blood.
In general, the CD4 count goes down as HIV disease progresses. Any single CD4 count value may differ from the last one even though your health status has not changed. You should not place too much importance on any one result. What is more important than any single value is the pattern of CD4 counts over time.
If your CD4 count declines over several months, your doctor may recommend beginning or changing anti-HIV treatment and/or starting preventive treatment for opportunistic infections like Pneumocystis carinii pneumonia (PCP). Your CD4 count should increase or stabilize in response to effective combination anti-HIV therapy.
According to public health guidelines, preventive therapy should be started when an HIV-positive person who has no symptoms registers a CD4 count under 200. Some physicians will opt to consider treatment earlier, at 350. The Centers for Disease Control and Prevention considers HIV-infected persons who have CD4 counts below 200 to have AIDS, regardless of whether they are sick or well.
Is there anything else I should know?
The CD4 count tends to be lower in the morning and higher in the evening. Acute illnesses, such as pneumonia, influenza, or
herpes simplex virus infection, can cause the CD4 count to decline temporarily. Cancer chemotherapy can dramatically lower the CD4 count. Regardless, it can be used as an effective monitoring tool if the more sensitive
HIV viral load test is not available.
The CD4 count does not always reflect how someone with HIV disease feels and functions. For example, some people with higher counts are ill and have frequent complications, and some people with lower CD4 counts have few medical complications and function well.
