Sequential antiretroviral adherence measurement using electronic bottle cap monitors in a cohort of HIV-infected adults.

Most studies employing electronic bottle monitors to measure antiretroviral adherence are limited to 24 weeks of duration, providing a snapshot of adherence from a treatment course that may be lifelong. The stability of these measures in individual patients over time has not been previously described. We measured antiretroviral adherence using Medication Event Monitoring System (MEMS) caps in a patient cohort in 2004 and 2005 and repeated the measurement in 2008 and 2009. Forty-eight participants completed both monitoring periods. Mean adherence rates in the first and second periods were 74.2% and 68.9%, respectively. Adherence rates from the 2 periods for individual participants were highly correlated (Spearman rho = .66, P < .001).