Development and assessment of psychometric properties of model medication adherence (MMA) questionnaire to measure adherence to oral medication among patients with type 2 diabetes mellitus

Abstract

INTRODUCTION: Medication adherence among patients with type 2 diabetes (DM) is assessed in everyday clinical practice. OBJECTIVES: To develop a questionnaire to measure adherence to oral medication among patients with DM and to assess its psychometric properties METHODS: The “Model Medication Adherence (MMA)” questionnaire was developed using the evidence from literature review and interviews with key stakeholders and patients. Answers were set on a five-point Likert scale that scored from 1 to 5, with 15-73 as the possible range of the total score. MMA was drafted in English and translated to Sinhala language by forward- backward translation. A descriptive cross-sectional study was carried out among adult patients with type 2 DM who attended clinics in Gampaha District General Hospital (DGH). A sample of 150 patients was recruited consecutively. The construct validity of MMA was assessed by Exploratory Factor Analysis (EFA) through Principal Component Analysis (PCA) with Varimax rotation RESULTS: EFA yielded four factors; sick role behaviour, autonomy, forgetfulness, and barriers that explained 64.36% of the variance of the total score of MMA. Internal consistency was acceptable (Cronbach’s alpha 0.73). The testretest reliability coefficient was 0.85 (p=0.01). Acceptability of the MMA was established by non-response items (none) and the time taken to complete (20 minutes). CONCLUSIONS & RECOMMENDATIONS: MMA is a simple valid questionnaire that adds a novel concept to the adherence literature; sick role and autonomy. It has a good factor structure with established construct validity and is recommended to be used in the clinical setting.