Measuring the amount of AIDS virus circulating in the blood of HIV-positive patients is not a good indicator of the health of their immune systems, researchers said on Tuesday.
Physicians often assess the amount of HIV particles in the blood — known as the viral load — along with the decline in CD4 cells that help the body fight infections to measure the disease's progress and decide when to prescribe drug therapy.
But a study of 2,800 untreated HIV-positive individuals found only about 5 percent of the variations in viral load corresponded to variations in immune system damage.
Depletion of CD4 cells is therefore not a simple consequence of the amount of virus circulating, said the study published in this week's Journal of the American Medical Association.
"The results of this nationwide study may have profound implications in our understanding of how HIV causes disease and in our approach to the management of HIV-infected patients," said lead investigator Dr. Benigno Rodriguez of Case Western Reserve University in Cleveland.
Estimating damage to the immune system is critical in deciding when it is best to start antiretroviral therapy, the AIDS-fighting drugs credited with allowing millions of infected people to live with the disease.
Because of issues of drug resistance and the potent side effects of the drugs, doctors and patients often defer starting medications until medically necessary.
The study challenges the current belief that the degree to which the virus replicates itself is the trigger for the loss of CD4 cells, white blood cells that are a key component of the body's immune system.
An accompanying editorial in the journal said the findings were exciting because they suggested that researchers should look for and target non-viral factors that set off the eventual decline in the immune system.