About half of all adults being treated for HIV infection in the United States have strains of the virus that are resistant to some of the standard drug therapies, according to a study released Tuesday.
The study is the first large-scale national survey to reveal the drug resistance. Previous drug-resistance research, physicians said, focused only on smaller groups of patients.
"This is very discouraging," said Dr. Samuel Bozette of the San Diego VA Medical Center, a co-leader of the study. "It really shows the breadth of the problem. This is something we'll have to take into account in future treatment plans and strategies."
The survey, coordinated by the Rand Corp. think tank in Santa Monica, tested blood samples of about 1,700 patients. More than three-quarters showed signs of resistance to one or more drugs frequently used to treat HIV. About 85% of the patients who were prescribed the type of therapy that often includes "cocktails" of three or more drugs had drug resistant strains of HIV.
In the past, many researchers believed the poor, the homeless and intravenous drug users were most likely to have resistant viruses because they might not properly use AIDS drugs. But this study revealed that "white males . . . , those with higher education and private medical insurance" were most likely to have drug-resistant viruses. Researchers also emphasized that drug-resistant strains of HIV can be transmitted by sexual contact.
Related studies have revealed that up to 20% of newly diagnosed HIV patients--even before they are prescribed drugs--have a strain of HIV that is drug-resistant, said Dr. Douglas Richman of UC San Diego, a co-leader of the study.
"We need to step up efforts to prevent transmission of drug-resistant virus, as this appears to be an increasing problem," he said.
Researchers were surprised by the study's numbers, which show the need for testing to reveal the specific drugs that won't work for the patient.
"There needs to be more use of drug resistance testing to manage patients who have failed treatment and who have been recently infected . . . ," Richman said. "We need new drugs that are effective against drug-resistant virus."
Researchers have found that unless HIV is completely suppressed, a resistance can develop, Bozette said. As a result, doctors have to be particularly careful about prescribing the right combination of drugs.
"Unless you knock out the virus completely, it will continue to multiply," Bozette said. "And that virus that multiplies is just the strain that will be resistant to the drugs you're taking."