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Quick, Simple Test Could Reduce HIV Drug Resistance

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WebMD Health News

Nov. 22, 2001 -- Knowing whether HIV drugs are working can ultimately mean the difference between life and death. Assessing drugs' effectiveness currently takes as long as two months, but findings reported this week by researchers from two federal health agencies suggest the process can be shortened to as little as a week.

Researchers from the National Institute of Allergy and Infectious Diseases (NIAID) and the National Cancer Institute found that the rate at which the AIDS virus disappears from the blood during the first week of treatment is a highly accurate measure of whether the drugs will fail. The report was published in the Nov. 24 issue of the medical journal The Lancet.

The preliminary research indicates that people who do not experience a five-fold, or 80%, drop in viral load by the sixth day of treatment will almost certainly have a poor long-term response to the chosen drugs.

"We found that if we didn't see a rapid drop in viral load during the first week, then there was a good chance that the drug regimen was not going to be effective," lead author Michael A. Polis, MD, of the NIAID, tells WebMD. "If we don't see a big drop, then it could mean that a patient isn't taking the drugs appropriately or it could mean resistance. Either way, the earlier we know this the better."

If confirmed and widely adopted, the simple measure could reduce drug resistance among people on HIV drugs. Side effects of treatment might also be minimized if doctors can more rapidly identify drug treatments that don't work.

There are currently around 17 different HIV drugs that have been approved by the FDA. They are given in a variety of combinations, because the fast-mutating virus quickly develops resistance to single drugs. Because many of the drugs are similar, resistance to one drug may mean resistance to several.

The most common way to test how well HIV drugs are working is by measuring the amount of virus in the blood after four to eight weeks of therapy. Using data from three previously reported trials, Polis and colleagues found that the five-fold or less drop in viral load at day six of therapy predicted treatment failure more than 99% of the time.

"This method is far better at identifying bad regimens than good ones," Polis says, adding that treatment response is not certain for those whose drop in viral load is more than six-fold but less than 50.

Co-author Dimiter S. Dimitrov, PhD, ScD, says the research team is in the process of analyzing ways to spot suboptimal treatments even earlier. He adds he is hopeful that measurements of drug concentrations in the blood will prove effective in identifying failing drug regimens in just a few days. Dimitrov is a computational biologist at the National Cancer Institute.

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