An adherence self-report questionnaire facilitated the differentiation between nonadherence and nonresponse to antihypertensive treatment

OBJECTIVES: To evaluate, among hypertensive patients, a brief adherence self-report questionnaire (ASRQ), using electronic monitors (medical event monitoring system, MEMS) as the gold standard comparator. STUDY DESIGN AND SETTING: A total of 239 patients with hypertension in five general practices in Bristol, UK completed the ASRQ before and at the end of the 4-week study period. Patients were asked to choose one of six descriptions (from level 1=perfect adherence to level 6=nonadherence) to express their medication taking. The main outcome measure was "timing adherence" (correct interdose intervals) as measured through electronic monitors. RESULTS: Most patients (89%) stated perfect or nearly perfect adherence, and data from the electronic monitors showed a mean timing adherence of 88.3% (n=216). Using the cutoff of those who reported ASRQ levels 1 and 2 (all tablets taken but not always at the same time of day), a high percentage of those with comparatively high adherence according to MEMS were correctly identified (specificity, 90-93%; negative predictive value, 66-96%). However, sensitivity (detection of true nonadherers) and positive predictive value were poor to moderate (14-42% and 22-66%, respectively). CONCLUSION: The questionnaire could be a useful aid to facilitate the difficult differentiation between nonadherence and nonresponse to prescribed antihypertensive medication.