Validity of a questionnaire for the detection of non-adherence in patients with complex medication regimens: a comparison with pill counts

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Philipp Harbig
I Barat
E M Damsgaard


Objectives: The purpose of the study was to validate the ability of a questionnaire to detect non-adherence in elderly primary healthcare Danish patients with complex medication regimens. Methods: The tested questionnaire comprised the 4-item Morisky Medication Adherence Scale (MMAS-4) with 10 additional supplementary questions. Non-adherence rates in 577 elderly Danish patients were determined by the questionnaire and compared with non-adherence rates estimated by pill count (PC) using contingency table analysis. The stability of the questionnaire was evaluated by test-retest reliability correlation analyses comparing the non-adherence rates of 222 participants at three visits (0, 6 and 12 months).Results: The MMAS-4 overestimated non-adherence (visit 2: 53%, visit 3: 55%) compared with the PC (visit 2: 15%, visit 3: 12%), as did the 14-item version of the questionnaire (visit 2: 29%, visit 3: 32%). Compared with the reference standard, the estimated sensitivity to detect non-adherence by the MMAS-4 at visit 2 was 47.9 (95% CI: 43.4-52.4); visit 3: 45.7 (41.3-50.1) and the specificity visit 2: 60.5 (49.3-70.8); visit 3: 61.2 (48.5-72.9). The sensitivity of the 14-item version was visit 2: 72.7 (68.5-76.6); visit 3: 68.8 (64.6-72.8) and the specificity visit 2: 39.5 (29.2-50.7); visit 3: 37.3 (25.8-50.0).Conclusion: MMAS-4 and MMAS-4 with 10 additional questions over-estimated non-adherence and did not appear valid for detection of non-adherence in elderly home living patients with complex medication regimens. The questionnaire may be a useful tool for preliminary detection of non-adherent patients as part of person-centered care, but cannot be recommended for screening of non-adherent drug intake.

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