Evaluation of the correlation between self-report and electronic monitoring of adherence to hypertension therapy.

Blood pressure (BP) control remains sub-optimal all over the world. Medication adherence is an important determinant of BP control. None of the available methods for measuring medication adherence is currently regarded as a universal consensus gold standard. In this study, we evaluated the correlation between self-report (Morisky's Medication Adherence Self-assessment Scale) and electronic (eCap) methods of medication adherence assessment. The self-report measure was administered at study entry while electronic compliance data was collected prospectively. Almost all (97.4%) of enrolled patients completed the study. Medication adherence scores ranged from 0 to 100% (69.33, ± 27.57) and 6.6-100% (66.92 ± 22.59) for Morisky's scale and eCap, respectively (Wilcoxon rank sum test, p = 0.253). Modal class interval for adherence scores were 61-80% (n = 28, 37.3%) and 81-100% (n = 23, 30.7%) for the eCap and Morisky's scale respectively. Overall, a weak correlation was found between the two methods (r = 0.056). The weak correlation was also maintained in subgroup analysis defined by attainment of BP control (r = 0.109 vs 0.0009), age (range r = -0.53 to 0.067), sex (0.009 to 0.151), level of education (-0.217 to 0.276), and Mini Mental State Examination score (-0.107 to 0.258). Our findings suggest that these methods are not equivalent in the evaluation of medication adherence.