Nonadherence to antiretroviral therapy is a substantial problem in HIV and jeopardizes the success of treatment. Accurate measurement of nonadherence is therefore imperative for good clinical management but no gold standard has been agreed on yet. In a single-center prospective study nonadherence was assessed by electronic monitoring: percentage of doses missed and drug holidays and by three self reports: (1) a visual analogue scale (VAS): percentage of overall doses taken; (2) the Swiss HIV Cohort Study Adherence Questionnaire (SHCS-AQ): percentage of overall doses missed and drug holidays and (3) the European HIV Treatment Questionnaire (EHTQ): percentage of doses missed and drug holidays for each antiretroviral drug separately. Virologic failure prospectively assessed during 1 year, and electronic monitoring were used as reference standards. Using virologic failure as reference standard, the best results were for (1) the SHCS-AQ after electronic monitoring (sensitivity, 87.5%; specificity, 78.6%); (2) electronic monitoring (sensitivity, 75%; specificity, 85.6%), and (3) the VAS combined with the SHCS-AQ before electronic monitoring (sensitivity, 87.5%; specificity, 58.6%). The sensitivity of the complex EHTQ was less than 50%. Asking simple questions about doses taken or missed is more sensitive than complex questioning about each drug separately. Combining the VAS with the SHCS-AQ seems a feasible nonadherence measure for daily clinical practice. Self-reports perform better after electronic monitoring: their diagnostic value could be lower when given independently.

Nonadherence to antiretroviral therapy (ART) jeopardizes good clinical outcome in people living with HIV. In a single-center prospective study, prevalence and correlates of nonadherence were investigated in 43 patients on ART. Nonadherence was assessed using Medication Event Monitoring System (MEMS), self-report and collateral report of treating physicians. Based on MEMS data, median taking adherence, dosing adherence, and timing adherence was 98% (interquartile range [IQR] = 5.3), 91.5% (IQR = 18), and 86% (IQR = 31.5), respectively. The median number of drug holidays per 100 days was 0.8 (IQR = 4.8). The prevalence of nonadherence measured by MEMS was 40%. Self-reported nonadherence and collateral report of nonadherence by physicians varied from 5% to 41% and 24% to 28%, respectively. Patients were categorized as adherent or nonadherent based on a clinically validated algorithm derived from MEMS parameters. Nonadherent patients used significantly more escaping coping strategies (p = 0.003) and planned problem solving strategies (p = 0.049), were prescribed significantly more antiretroviral medications (p = 0.02) and were significantly longer on ART (p = 0.04) than adherent patients. Identified correlates of nonadherence may help clinicians in detecting patients with HIV at risk for nonadherence and can support the development of adherence enhancing interventions.

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