Placebo practice trials: the best predictor of adherence readiness for HAART among drug users?

This study assessed the utility of a placebo practice trial in determining adherence readiness among drug users.

Participants with histories of drug dependency completed a 2-week practice trial that mimicked HAART (Phase 1), followed by a 2-week observation of adherence to HAART (Phase 2) for those who began antiretroviral therapy during the study period. The primary measure of adherence was electronic monitoring.

There were 201 participants enrolled; 39% met criteria for current drug dependency. Mean adherence to the practice trial was 67%. Of the 184 Phase 1 completers, 83 (45%) initiated HAART prior to the end of the study. Mean adherence to HAART was 74%, including 33 patients (39%) with 90+% adherence. Adherence to the practice trial was correlated with antiretroviral adherence (r =.49, p <.001), and 90+% adherence to the practice trial was an accurate marker of the "adherence readiness" (ability to adhere 90+% on HAART) of 72% of the participants. In multivariate analyses, practice trial adherence was the best independent predictor of antiretroviral adherence, accounting for 19% of the explained variance; other predictors included adherence to recent clinic appointments, cognitive functioning, unstable housing, and adherence self-efficacy.

These findings suggest that a brief placebo practice trial has the potential to provide clinicians and patients with an accurate screening tool for evaluating adherence readiness.