Validation of the Turkish version of the DOSE-Nonadherence measure among patients with cardiometabolic conditions.

WHAT IS KNOWN AND OBJECTIVE: There are no validated self-report measures to assess extent of and reasons for medication nonadherence in the Turkish language. The aim of this study is to evaluate validity and reliability of the Domains of Subjective Extent of Nonadherence Scale, which assesses extent of and reasons for nonadherence in Turkish patients with hypertension, diabetes mellitus and/or dyslipidaemia in community pharmacy settings. METHODS: The Turkish version of the DOSE-Nonadherence scale was developed through translation and cultural adaption. Psychometric properties of the scale were evaluated in a cross-sectional study among 203 patients who visited six community pharmacies located in Istanbul, Turkey between November 2020 and March 2021. For the extent of nonadherence domain, reliability was estimated through Cronbach's alpha, and convergent validity was evaluated with Spearman's rank correlation with the validated Turkish version of the Medication Adherence Report Scale (MARS). Reasons for nonadherence were characterized among participants reporting nonadherence to the extent of nonadherence items. The measure was administered at baseline and 2 weeks later to 30 patients to estimate stability of extent scores using the Wilcoxon test and intraclass correlation coefficient. p < 0.05 was set as the level of statistical significance. RESULTS: Among the 203 participants (65 male), the median (25th-75th percentiles) age was 59.0 years [51.0-67.0]. Cronbach's alpha for the extent of nonadherence scale was 0.86. A moderate negative correlation (r = -0.58; p < 0.001) was found between the extent of nonadherence scores and MARS, supporting convergent validity. The most common reasons for medication nonadherence were forgetfulness (22.5%) and mismatch between the patients' daily routine and medication taking (17.5%). The intraclass correlation coefficient was 0.97 for extent of nonadherence scores at baseline and 2 weeks (p < 0.001). WHAT IS NEW AND CONCLUSION: The DOSE-Nonadherence Scale could be used to identify nonadherent patients and their reasons for nonadherence in Turkish patients with chronic cardiometabolic conditions. This scale can be used to evaluate clinical pharmacist-led services to reduce medication nonadherence. Nonadherence could be recorded longitudinally in electronic health records to provide a more accurate picture of medication use. Pharmacists or other providers could administer interventions tailored to patients' reasons for nonadherence.