Tabriz University of Medical Sciences Health Promotion Perspectives 2228-6497 13 3 2023 09 11 Medications Non-adherence Reasoning Scale (MedNARS): Development and psychometric properties appraisal 212 218 10.34172/hpp.2023.26 EN Hamid Allahverdipour https://orcid.org/0000-0003-3700-6185 Majid Badri Abdolreza Shaghaghi https://orcid.org/0000-0002-3884-1847 Hassan Mahmoodi https://orcid.org/0000-0002-1234-9037 Haleh Heizomi https://orcid.org/0000-0001-6665-5497 Shayesteh Shirzadi https://orcid.org/0000-0002-0914-4989 Mohammad Asghari-Jafarabadi https://orcid.org/0000-0003-3284-9749 Journal Article 10.34172/hpp.2023.26 2023 05 06 2023 06 21 Background: Proper elucidation of medication non-adherence reasoning especially in older adults might pave the way for an auspicious therapeutic outcome. The main aim of this study was to develop and psychometrically test the Medications Non-adherence Reasoning (MedNARS) questionnaire for application in research and probably practice settings. Methods: A mixed methods design was utilized to develop the MedNARS. The item pool was mainly generated based on a qualitative query and literature review. The expert panel approved version of the MedNARS was psychometrically assessed on a convenience sample of 220 older patients with chronic disease. The internal consistency, test-retest reliability, content and face validity of the scale were appraised and its construct validity was assed using exploratory and confirmatory factor analyses. Results: A nine-item version of the MedNARS was drafted based on the classical item analysis procedures and its estimated internal consistency measure of the Cronbach’s alpha (0.85) and test-retest reliability (0.96) were in the vicinity of acceptable range. The exploratory factor analysis (EFA) output revealed a unidimensional structure for the MedNARS and the conducted confirmatory factor analysis (CFA) indicated an acceptable data fit for the extracted one-factor model. The goodness of fit indices were as the followings: χ2 /df=1.63(90% CI: 0.02 to 0.11), root mean squared error of approximation (RMSEA)=(0.07), comparative fit index (CFI)=0.95, Tucker–Lewis index (TLI)=0.93 and standardized root mean squared residual (SRMSR)=(0.05). Conclusion: The study findings were indicative of MedNARS’s applicability and feasibility for use in assessment of medication non-adherence reasoning among the elderly patients with chronic diseases. The MedNARS as a brief and elder-friendly instrument can be applied both in research and practice settings to enhance efficiency, safety, and health outcomes of the therapeutic recommendations.