Validation of the 5-Item Medication Adherence Report Scale in Older Stroke Patients in Iran

Background: There is a lack of feasible and validated measures to self-assess medication adherence for older patients with stroke. In addition, the potential determinants of medication adherence for older patients with stroke remain unclear. Objectives: The aims of this study were to (1) examine the psychometric properties of a 5-item questionnaire on medication adherence, specifically the 5-item Medication Adherence Report Scale (MARS-5), and (2) explore the determinants of medication adherence. Methods: Stroke patients older than 65 years (N = 523) filled out the MARS-5 and the Hospital Anxiety and Depression Scale. The medication possession rate (MPR) was calculated to measure the objective medication adherence. Several clinical characteristics (stroke types, blood pressure, comorbidity, HbA1c, quantity of prescribed drugs, fasting blood glucose, and total cholesterol) and background information were collected. We used Rasch analysis with a differential item functioning test to examine psychometric properties. Results: All 5 items in the MARS-5 fit in the same construct (ie, medication adherence), no differential item functioning items were displayed in the MARS-5 across gender, and the MARS-5 total score was strongly correlated with the MPR (r = 0.7). Multiple regression models showed that the MARS-5 and the MPR shared several similar determinants. In addition, the variance of the MARS-5 (R-2 = 0.567) was more than that of the MPR (R-2 = 0.300). Conclusions: The MARS-5 is a feasible and valid self-assessed medication adherence for older patients with stroke. In addition, several determinants were found to be related to medication adherence for older patients with stroke. Healthcare providers may want to take heed of these determinants to improve medication adherence for this population.