Abstract
Introduction: One major cause of uncontrolled hypertension is poor medication adherence. Yet, clinicians are poor at judging adherence and the gold standard for measuring medication adherence - electronic monitoring - is rarely available in clinic settings. Self-report adherence questionnaires, by contrast, are free, simple to administer, and may be useful for screening. Hypothesis: To compare the test properties of the Morisky Medication Adherence Questionnaire (MMAQ) and the Visual Analog Scale (VAS) for diagnosing non-adherence in patients with uncontrolled hypertension, using electronic pillbox monitoring as the gold standard. Methods: Thus far, 48 patients with uncontrolled hypertension [BP ≥140/90 mmHg (or ≥130/80 mmHg if diabetic) on 2 serial clinic visits] have been enrolled during visits to a hospital-based primary care practice. Patients are asked to take up to 4 of their BP medications from a 4-bin electronic pillbox (MedSignals) that records the date and time each bin is opened. At the next visit, patients complete the MMAQ, comprised of 8 brief questions that assess pill-taking behavior. The MMAQ is scored from 0 to 8; 8 signifies perfect adherence. Patients also complete the VAS by marking an “X” on a line from 0% to 100% to indicate how often they took each of their BP medications. Sensitivity, specificity, and negative likelihood ratio (NLR) were assessed for each test. The gold standard for adherence was ≥ 80% adherence averaged across each of the electronically monitored medications. Results: Mean age is 62 years (range 34 [[Unable to Display Character: –]] 83), 70% women, 62% Hispanic, 52% Black, and 50% with diabetes. Mean BP at enrollment was 160/88 mmHg. Patients were prescribed a mean (SD) of 2.6 (0.9) BP medications. Adherence was monitored for 41 +/- 23 days. Mean adherence by electronic monitoring was 78% (range 13%-100%); 42% were adherent (≥ 80%) by the gold standard. Using a cutpoint of 7.5 (67% of the sample were below this cutpoint), the MMAQ has a sensitivity of 94% and specificity of 54%, corresponding to a NLR of 0.10 (95%CI 0.01 to 0.67). Using a cutpoint of 80% (only 11% of the sample below this cutpoint), the VAS has a sensitivity of 28%, specificity of 67%, and a NLR of 0.72. Conclusions: The MMAQ, but not the VAS, is a sensitive tool for screening for non-adherence in patients with uncontrolled hypertension and may be useful for excluding medication non-adherence as the cause of uncontrolled hypertension for a large proportion of patients.
Published Version
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