New tests are helping identify treatment-resistant strains of the AIDS virus, allowing doctors to customize the drug cocktails given to their patients.
The AIDS virus rapidly mutates (changes genetically) to resist the drugs thrown at it. As a result, some patients get no prolonged relief from their first try on the powerful combinations of drugs now available against HIV.
To help doctors find an effective combination, scientists are developing resistance tests and marketing them.
But the tests do not have a long enough track record to be used routinely, a panel assembled by the International AIDS Society-USA said in Wednesday's Journal of the American Medical Association.
Until more study, the tests are appropriate only in certain situations, said the team, led by Dr. Martin S. Hirsch, director of clinical AIDS research at Massachusetts General Hospital.
There are two types of tests: one that looks for genetic mutations that have known drug resistance, and another that directly measures whether a drug will kill the AIDS virus taken from an individual patient.
HIV treatment usually involves two older drugs and one of the newer class of medicines called protease inhibitors. Such cocktails have revolutionized therapy, reducing the virus to nearly undetectable levels in the body.
Resistance to such cocktails is still relatively rare, and routinely screening HIV-positive patients before starting them on treatment is not justified, the panel said.
Resistance tests are best used to guide therapy after initial treatment fails and all other possible causes of treatment failure are ruled out, the panel said.
An AIDS researcher not on the panel agreed that the tests should be used judiciously. Dr. Douglas L. Mayers, head of the Viral and Ricksettial Disease Program at the Naval Medical Research Institute in Bethesda, Md., also noted that the tests cost less than the $1,000 typically spent on one month of drug cocktails.
The International AIDS Society-USA is an independent, nonprofit organization in San Francisco.
Written by Brenda C. Coleman
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