Day one:
After you've tested positive

May 2008 View PDF En español

Common blood tests and what they tell you

CD4 cell count tests

For many years, testing the number of CD4 cells was the only lab measure for the effects of HIV disease. Low numbers of these cells (below 200) accurately predict the risk of major infections.

Doctors encourage people to start HIV therapy when their CD4 counts are 200–350. However, these are arbitrary numbers used in studies of HIV drugs. By itself, a CD4 count doesn’t tell us enough about the state of disease. It only shows that the level of CD4 cells is below normal, to varying degrees. Getting the full picture of your HIV disease requires monitoring your general health and additional tests, especially the viral load test and CD4 percentage.

It has become common to put people with CD4 counts below 200 or 300 on preventive treatment for PCP (often using Bactrim/Septra or dapsone), along with all people who have had an initial bout of PCP. Regardless of CD4 count, yearly checking for tuberculosis is becoming increasingly important. Prevention strategies for all of the common OIs are described in Project Inform’s publications, Opportunistic Infections Chart and Strategias for Managing Opportunistic Infections.

CD4 Cell Count Ranges
Normal	Below normal	Low
(500 plus)	(350–500)	(under 350)

Normal Range:
In general, a CD4 count above 500 suggests no immediate danger. This level is sometimes used as the bottom of the “normal” range, but this can be misleading. While an occasional drop to 500 may be normal, a steady or falling count over time towards 500 or even 600 is not normal and suggests a weakened immune system. At the very least, nutritional counseling, CD4 count monitoring and using other routine tests are recommended in this range, whether or not treatments are used.

Below Normal Range:
CD4 counts in this range indicate significant decline of the immune system. However, serious symptoms are uncommon. It is quite rare for a person to die of AIDS with CD4 counts in this range. Some researchers believe this is the best time to begin treatment, especially if your viral load tests also indicate significant viral activity.

Low Range:
A CD4 count of 200 or less constitutes an AIDS diagnosis. CD4 counts below 350 indicate the greatest risk for infections. A person with counts below 350 may remain stable for many years, especially with thoughtful health care. While some people have warning signs (symptoms) before major infections occur, this is not always the case. Some progress directly from apparently good health to serious OIs. Generally, people with established HIV infection with CD4 counts in this range are encouraged to start HIV therapy.

Viral load tests (PCR)

Tests are available that directly measure the activity of HIV in the blood. They provide extra information to describe a more accurate picture of the risk of disease progression.

Viral load tests measure the amount of new HIV being produced and released into your blood. Studies show that higher viral loads are associated with a greater risk of losing CD4 cells and then progressing to symptoms of HIV disease. Ideally, an HIV-infected person should have no detectable level of virus, which means that HIV activity is too low to be measured by the tests.

Current tests measure down as low as 50 copies of virus. This is associated with the best possible medical outcome. Higher levels — ranging from about 30,000 (in women) to 60,000 (in men) to upwards of millions of copies of virus — are linked to higher rates of disease progression. In short, the higher the number, the more rapid the rate of disease progression.

Studies of new drugs use viral load tests to measure the effects of the drugs. A good combination of HIV drugs can quickly reduce the level of virus at least ten times and often as much as a thousand times. The goal of therapy is to reduce viral load to as low as possible, preferably below the lowest level detected by the test, below 50 copies.

HIV-positive people and their doctors use both CD4 counts and viral load tests to make decisions about if and when to use HIV drugs. These tests also help determine whether a drug is working or not. When HIV levels begin to rise again while using a drug, most doctors believe it is time to switch to another drug or combination of drugs. Also, if your CD4 counts begin falling, reassessing your HIV therapy is warranted.

At the very least, viral load tests provide a rational basis for helping some to decide when or whether to use HIV drugs, as well as a tool for determining whether or not a drug combination is working. For more information, read Project Inform’s publications, Blood Work: A Useful Tool for Monitoring HIV and Blood Work: Two Common Tests to Use.

Final thoughts on testing

No single test gives a total picture of immune health or disease progression, but CD4 count and viral load test results taken together over time are very important. As we learn to manage HIV as a chronic illness, these tests provide rational guidance about what treatments to use, when and when not to use them, and how well they’re working. To help you chart these various blood tests, use Project Inform’s publication, Personal Tracking Charts.

Strategy for HIV disease

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