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Agency for Healthcare Research Quality

HIV/AIDS Research

Updated pharmacy data can track whether HIV patients are maintaining enough adherence for treatment success

Patients must adhere to antiretroviral therapy more than 95 percent of the time in order to have the best chance of maintaining HIV suppression. Lower medication adherence, which can be uncovered by data on patient drug refills, can clue clinicians that intervention may be needed to boost suppression of HIV, suggest researchers at the University of Pennsylvania Center for Education and Research on Therapeutics. They examined a population-based group of HIV-infected adults residing in British Columbia, Canada, who started receiving antiretroviral therapy between August 1, 1996, and September 30, 2003. These adults had at least two consecutive viral loads less than 500 copies/mL (undetectable) and had antiretroviral prescriptions filled at least 3 times during a followup period ending September 30, 2004.

The researchers defined treatment failure as the second of two consecutive viral loads more than 1000 copies/mL, the clinical cutoff for maintaining a treatment response to antiretroviral drugs. Among the 1,634 HIV-infected adults who began triple combination antiretroviral therapy during the study, 37 percent had a rebound in HIV load (treatment failure), with a median time to rebound of 22 months.

After accounting for other factors that might confound the relationship between drug adherence and viral failure (for example, CD4 cell count, injection drug use, age, and sex), adults with 95 percent or less adherence to antiretroviral medication were 1.66 times more likely to experience treatment failure than those with greater than 95 percent adherence. Overall, 34 percent of those with more than 95 percent adherence had virological failure compared to 41 percent of those with 70 to 95 percent adherence and 63 percent of those with less than 70 percent adherence. The study was supported in part by the Agency for Healthcare Research and Quality (HS10399).

See "A simple, dynamic measure of antiretroviral therapy adherence predicts failure to maintain HIV-1 suppression," by Robert Gross, M.D., M.S.C.E., Benita Yip, Vincent Lo Re III, M.D., and others, in the October 15, 2006, Journal of Infectious Diseases 194, pp. 1108-1114.

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