Development and Initial Psychometric Evaluation of a Family Functioning Questionnaire for Diabetes Self-Management Based on the McMaster Family Functioning Model: Evidence from Indonesia

Background: Family functioning can play a crucial role in supporting diabetes self-management; however, validated instruments specifically designed to assess family functioning in diabetes self-management and systematically grounded in a comprehensive family functioning theory remain limited. Objective: This study aimed to develop and evaluate its initial psychometric properties of the Family Functioning Questionnaire for Diabetes Self-Management (FF-DMSM), a theory-based instrument derived from the McMaster Family Functioning Model. Methods: This methodological study involved instrument development, content validation, exploratory structural validity, and reliability testing. Content validity was evaluated by an expert panel using the Content Validity Ratio (CVR) and Content Validity Index (CVI). Exploratory structural validity was examined through exploratory factor analysis (EFA) using principal axis factoring with Varimax rotation. Internal consistency reliability was examined using Cronbach's alpha. The questionnaire was administered to community-dwelling adults with diabetes who had practiced self-management for at least one year. Results: The FF-DMSM consisted of 30 items across six domains: problem solving, communication, roles, affective responsiveness, affective involvement, and behavior control. Content validity was supported by a high scale-level CVR (S-CVR/Ave = 0.87). The scale-level CVI demonstrated excellent content validity for relevance (S-CVI/Ave = 0.91), clarity (S-CVI/Ave = 0.92), and simplicity (S-CVI/Ave = 0.92). Exploratory factor analysis suggested a preliminary six-factor structure consistent with the theoretical model, with all items showing satisfactory factor loadings. The instrument demonstrated high internal consistency, with Cronbach's alpha values indicating acceptable to excellent internal consistency at both the total scale and subscale levels. Conclusion: The FF-DMSM provides initial evidence of content validity, exploratory structural validity, and internal consistency of instrument for assessing family functioning in diabetes self-management. However, the six-factor structure should be interpreted as preliminary and requires further confirmation using confirmatory factor analysis in an independent sample, together with additional validity testing.