Similar adherence rates favor different virologic outcomes for patients treated with nonnucleoside analogues or protease inhibitors

Abstract

Background: This prospective study verified the effect of adherence on the risk of virologic failure.

Methods: At enrollment in the study, a total of 543 patients who were following a steady (duration, >or=6 months) and effective (viral load, <50 human immunodeficiency virus [HIV] RNA copies/mL) regimen of highly active antiretroviral therapy (HAART) completed a self-reported questionnaire derived from the Adult AIDS Clinical Trials Group Adherence Follow-up Questionnaire. Patients were followed up for the subsequent 6 months to document virologic failure, which was defined as 2 consecutive viral load measurements of >500 HIV RNA copies/mL.

Results: Only the type of treatment and the adherence rate at baseline were significantly associated with the virologic end point. Among patients who reported an adherence rate of <or=75%, the rate of virologic failure was 17.4%; this rate decreased to 12.2% for patients whose adherence rate was 76%-85%, to 4.3% for patients whose adherence rate was 86%-95%, and to 2.4% for patients whose adherence rate was >95%. When analysis was adjusted according to the type of regimen received, patients who were receiving protease inhibitor (PI)-based HAART and who had an adherence rate of up to 85% had a virologic failure rate of >20%, whereas, only for patients who were receiving nonnucleoside reverse-transcriptase inhibitor (NNRTI)-based HAART and who had an adherence rate of <or=75%, the virologic failure rate was >10%. For the comparison of NNRTI-treated patients and PI-treated patients with an adherence rate of 75%-95%, the odds ratio was 0.157 (95% confidence interval, 0.029-0.852). The number of pills and daily doses received correlated with the reported adherence rate.

Conclusions: Patients receiving NNRTIs report a higher rate of adherence than do patients receiving PIs. Adherence is significantly influenced by the number of pills and daily doses received. Low adherence is a major determinant of virologic failure; however, different therapies have different cutoff values for adherence that determine a significant increment of risk.