Questions about HIV Causing AIDS? Viral Load and T-Cell (CD4) Counts: Why They Really Matter.

If you are being treated for HIV or AIDS, your doctor uses a number of blood tests to check how you're doing. One of the most important tests measures viral load, the amount of HIV in your blood. Another very important test counts your CD4 cells, sometimes called T-cells. CD4 cells are a key part of your body's disease-fighting defenses, called the immune system.

But some people claim that HIV doesn't really cause AIDS. These people, known as "AIDS deniers," "denialists" or "AIDS dissidents," also say that viral load and CD4 tests are meaningless. They claim these tests don't really tell anything about your health, and that they might even hurt you by frightening you for no reason.

What Do Viral Load and CD4 Tests Really Tell Us?

What are CD4 Cells?

CD4 cells help to organize your body's defenses against disease. Doctors can take a sample of your blood and count the number of CD4 cells. Healthy adults and teenagers usually have a CD4 count of at least 800 cells per cubic millimeter of blood (a cubic millimeter is a very small amount, roughly one small drop).

What does HIV do to CD4 counts?

HIV attacks CD4 cells, and as time goes by people with HIV often see their CD4 counts drop. The lower your CD4 count, the greater your chances of getting a number of very serious diseases. When your CD4 count is below 200, the risk of illness becomes severe.

I've heard that you can have a low CD4 count and still be healthy. Is that true?

While there have been a few medical reports of people who seemed healthy even though they had very low CD4 counts, these cases are rare. Research overwhelmingly shows that people with low CD4 counts are much more likely to get sick than people who have a normal amount of CD4 cells.

The AIDS denialists who claim that CD4 counts are meaningless often point to a study of AIDS patients called the Concorde study, in which people who had a small increase in CD4 counts did not live longer than those whose CD4 counts stayed the same. But that study was done nearly 10 years ago, before modern combination therapy, and the CD4 increases were very small. Newer studies with more potent treatments show that a big boost in CD4 cells almost always lowers the risk of getting seriously ill.

For example, the deadly pneumonia called PCP occurs much more often in people with very low CD4 counts. In one study with over 1,000 patients, almost everyone who got PCP had a CD4 count below 200. Study after study has shown the same thing: The lower your CD4 count, the greater your chance of getting PCP or other serious infections.

The AIDS denialists leave out these important facts.

Why are viral load tests used?

CD4 counts give you and your doctor a good idea of how much damage HIV has done to your immune system. But you also need to know how fast that damage is happening. Viral load tests, which tell the doctor how much HIV is in your blood, are a very important clue to how quickly HIV is doing harm.

These tests go by several different names, like PCR (polymerase chain reaction) or bDNA (branched DNA), but they all work roughly the same way. They count HIV's genetic material--the building blocks of the virus

What does viral load tell us?

People with a high viral load are much more likely to get sick or die of AIDS than people with a low viral load.

The AIDS denialists sometimes suggest reasons why these tests might give a wrong answer. They point to a few old reports, from when viral load tests were new and still experimental, as evidence that they don't work. But there is a huge pile of newer evidence showing that viral load tests work extremely well. Many studies have shown that people with high viral loads are more likely to get sick or die from AIDS-related illnesses than people whose viral load is lower.

For example, one very important study has followed thousands of gay men since 1984. A few years ago researchers did viral load tests on the very earliest blood samples from that study and then looked at how many of those patients were still alive. The men with the highest viral loads were 77 times more likely to have died of AIDS than those with the lowest viral loads. Other studies in the U.S. and Europe have shown the same thing: A higher viral load almost always means a higher risk of sickness and death.

What happens when treatment reduces my viral load?

Studies have shown that when treatment reduces your viral load, it also reduces your chance of getting an AIDS-related infection or dying. Recently, a group of expert scientists reviewed 18 studies of anti-HIV drugs, which involved over 5,000 patients. Over and over again they found the same thing: The more viral load was reduced, the healthier the patients stayed.

The Bottom Line

No medical test is perfect, and mistakes or misunderstandings sometimes happen. You should always go over your test results carefully with your doctor to make sure you understand them.

But the people who claim that viral load and CD4 tests are useless are not telling the truth. These tests give you and your doctor important information that can help you make the best treatment choices.