Once upon a time, viral load tests confused the hell out of everybody. It wasn’t until official usage guidelines were produced by major medical organizations, such as the International AIDS Society-USA (IAS-USA) and the United States Public Health Service (USPHS), that the cloud of uncertainty began to lift. Now drug-resistance testing, a technological breakthrough that helps determine which drugs may not work against your virus, has many doctors and people with HIV scratching their heads. Luckily, the IAS-USA has just extended a helping hand with resistance-testing guidelines, published in May in the Journal of the American Medical Association (available at www.iasusa.org).

Two types of drug-resistance assays (tests) are available: genotypic, which examines HIV’s genetic structure for mutations (changes) that may lead to drug resistance, and phenotypic, which actually tests the virus’ ability to reproduce in the presence of each approved anti-HIV drug (see “Play It as It Lays,” POZ, January 2000). Usage guidelines were needed, says IAS-USA panelist Martin Hirsch, MD, of Harvard Medical School, “to help caregivers and payers determine when resistance testing is justified.”

According to the IAS-USA, drug-resistance testing should be “considered” for recently infected HIVers to determine if transmission involved a drug-resistant strain of the virus; it is “recommended” for PWAs whose first or subsequent HAART combination is failing, preferably before stopping or switching the faulty regimen.

But which test to take? “We don’t think there are sufficient comparative data to choose between one assay and another at this time,” Hirsch says. “Hopefully, studies underway or planned will provide the necessary information for people with HIV to make informed choices.”