The prevalence of antiretroviral drug resistance in the United States.

Background: Antiretroviral therapy has dramatically reduced the morbidity and mortality of infection due to HIV. The emergence of drug-resistant virus has limited the usefulness of many drugs. Objective: To determine the prevalence of HIV drug resistance in the population of adults receiving care in the United States. Design and methods: HIV drug susceptibility assays were performed on plasma virus from a random sample representative of the 132 500 HIV-infected American adults who had received medical care in early 1996 yet were viremic with > 500 copies/ml of HIV RNA in late 1998. A blood sample was obtained from 1797 patients who comprised a representative sample of the 208900 adults receiving urban care for HIV infection in early 1996 who survived to late 1998. The sampling procedure permitted weighting each evaluated patient to reflect demographic and other characteristics of the target population. Results: We estimated that 132 500 (63%) of the target population had HIV viremia of > 500 copies/ml. Among viremic patients, an estimated 76% had resistance to one or more antiretroviral drugs. The odds of resistance were significantly higher in patients with a history of antiretroviral drug use, advanced HIV disease, higher plasma HIV viral load and lowest CD4 cell count by self-report. Conclusions: The frequent selection for drug-resistant virus among viremic patients during the first 3 years of widespread use of potent antiretroviral combination therapy has significant implications for HIV treatment and transmission.