Patterns of antiretroviral therapy adherence and impact on HIV RNA among patients in North America.

OBJECTIVE: Adherence to antiretroviral therapies (ART) is the strongest predictor of viral suppression among individuals infected with HIV, however, limited data exists to understand the patterns of adherence that confer the greatest benefit across different ART regimens.

DESIGN: Longitudinal data pooled from 16 studies conducted between 1997 and 2009 across the United States.

METHODS: Adherence was measured using Medication Event Monitoring System. Percentage of time with sufficient drug concentrations (covered time) and the length of the longest treatment interruption during the 28 days prior to plasma HIV-RNA measurements were calculated. Logistic regression with generalized estimating equations was used to estimate medication-specific adherence estimates on detectable HIV-RNA (>400 copies/ml).

RESULTS: One thousand and eighty-eight participants with 3795 HIV-RNA measures were studied. Both lower covered time and greater longest interruption showed dose-response relationships with the odds of detectable HIV-RNA; however, estimates did not vary by medication regimen. Compared with 93-100% coverage, periods of 0-25% covered time had a three-fold increased risk of detectable HIV-RNA [odds ratio (OR) = 3.22, 95% confidence interval (CI): 2.48-4.19]. Similarly, compared to longest interruptions of 0-48 h, longest interruptions of 21-28 days had a nearly four-fold increased risk of detectable HIV-RNA (OR = 3.65, 95% CI: 2.77, 4.81).

CONCLUSION: We found that adherence was consistently strongly associated with treatment response across ART regimens. Of the patterns of adherence, longer interruptions may have greater impact than covered time. Future research should investigate additional methods for examining adherence patterns, understanding the determinants of consecutive missed doses and the evaluation of interventions designed to address interruptions in treatment.