Accuracy of measures of medication adherence in a cholesterol-lowering regimen.

This study examined the concordance between multiple measures of adherence, as well as sensitivity to detection of poor adherers, specificity, and predictive validity using a daily cholesterol-lowering regimen. Participants (N = 180) aged 24 to 60 years participated in an adherence ancillary study in a clinical trial. Males constituted 53.9% of this well-educated, community sample. Data on adherence were collected over a 6-month period, using electronic monitoring, self-report, specific recall, and pill counts. Electronically monitored (odds ratio [OR] = 5.348) and Shea self-report (OR = 2.678) predicted cholesterol lowering. Days (78.9%) and intervals (84.2%) adherent and the Shea (73.7%) were sensitive to the detection of poor adherers. Moderate associations were found between measures of the same type. Low correlations were found otherwise. The electronic monitor was the most accurate and informative measure. The Shea self-report was the most accurate brief, global estimate of adherence. Other measures were not associated with clinical outcome or sensitive to poor adherence.