Rationale, aims and objectives: To translate in German the 8-item Morisky Medication Adherence Scale (MMAS-8D). To validate it against objective and subjective measures of adherence in cardiovascular patients with polypharmacy.
Methods: A standard forward-backward procedure was used to translate the MMAS-8 into German. Validation took place on a convenience sample of ambulatory patients on chronic antiplatelet therapy between June 2010 and June 2011. Objective adherence was obtained from electronically monitored multi-drug punch cards. Internal consistency was assessed using Cronbach's alpha coefficient, construct validity using exploratory factor analyses and correlations between MMAS-8D and related measures. Convergent validity was assessed with a subjective questionnaire about beliefs about medicines (BMQ Specific, two sub-scales).
Results: A total of 70 patients were included (mean age 65.7 ± 9.9 years; 31.4% women). The mean score of the MMAS-8D was 7.5 (SD 0.8; range 4.5-8). Moderate internal consistency (alpha = 0.31) was observed due to multidimensionality of the scale. Factor analysis yielded four components that accounted for 71.7% of the total variance. Convergent validity was supported by significant correlations with BMQ Necessity (r = 0.31, P < 0.01), BMQ Concerns (r = -0.16, P < 0.05) and with electronic adherence reports (U-values 44 and 471, P < 0.05). Platelet aggregation values were within therapeutic range for 80% of the patients. Blood values of the antiplatelet agent within therapeutic range were associated with a higher MMAS-8D score (U-value 125, P < 0.05).
Conclusions: The German MMAS-8 appears to be a reliable instrument to catch medication adherence in cardiovascular patients. It may be useful in patients with chronic therapy for detecting non-adherence.
Keywords: German version; adherence; questionnaire; validation.
© 2015 John Wiley & Sons, Ltd.