title: Psychometric properties of the 8-item Morisky Medication Adherence Scale in patients taking warfarin.
abstract: There is no patient-reported medication adherence measure that has been validated in Singapore. This study aimed to validate the 8-item Morisky Medication Adherence Scale (MMAS) in patients taking warfarin in Singapore. A cross-sectional survey was conducted in a convenience sample of 151 patients taking warfarin at an anticoagulation clinic in 2011. Respondents completed the MMAS in English or Chinese depending on their preference. The MMAS had a Cronbach's alpha of 0.56 and good criterion-related validity as the scale scores were associated with warfarin refill rates (p = 0.04). Respondents with higher MMAS scores were found to have a higher percentage of International Normalised Ratios (INRs) within the therapeutic range (p = 0.01), higher adherence to diet recommendations (p = 0.02), and less perceived difficulty in taking all medications (p < 0.001); they were also more likely to take warfarin at the same time every day (p < 0.001). Confirmatory factor analysis showed that the eight items loaded onto one factor (RMSEA = 0.03). The sensitivity, specificity, positive predictive value and negative predictive value of the MMAS for identifying patients with poor INR control were 73.0%, 35.6%, 49.5% and 60.5%, respectively, using the time in the therapeutic INR range as the gold standard. This study shows that the 8-item MMAS has good validity and moderate reliability in patients taking warfarin. Future research is needed to investigate the scale's psychometric properties in other patient populations and clinical settings.
authors: Department of Pharmacy, Faculty of Science, National University of Singapore, Singapore.
authors: Ye
authors: Y
authors: Wang
authors: Ming Chai
authors: MC
authors: Kong
authors: Yu
authors: Y
authors: Ko
mesh_terms: D000328:Adult; D000368:Aged; D000925:Anticoagulants / Q000008:administration & dosage; D003430:Cross-Sectional Studies; D005260:Female; D006801:Humans; D019934:International Normalized Ratio; D007802:Language; D008297:Male; D055118:Medication Adherence / Q000523:psychology; D008875:Middle Aged; D011594:Psychometrics; D015203:Reproducibility of Results; D012846:Singapore; D011795:Surveys and Questionnaires; D014859:Warfarin / Q000008:administration & dosage*; D016903:Drug Monitoring
chemical_list: D000925:Anticoagulants; D014859:Warfarin