Development and validation of the Participation in Treatment Decision-Making Scale for Adults with Malocclusion (PTDMS-AM)

Background Participation in decision-making is crucial for patients with malocclusion. It is important to assess the extent to which patients are actively involved in such decision-making. Therefore, this study developed an instrument that evaluates patient participation in treatment decision-making among adults with malocclusion and tested its reliability and validity. Methods A cross-sectional instrument-development methodological approach was adopted. Guided by the concept of participation and shared decision-making theory, an initial scale was developed through literature analysis, qualitative interviews, expert evaluation, and a pre-survey. From September to December 2023, 257 patients from three tertiary general hospitals in Shanghai were selected for a questionnaire survey, item analysis, and exploratory factor analysis. From January to May 2024, 269 patients from these hospitals were selected to conduct a questionnaire survey for confirmatory factor analysis and criterion-related validity. Results The final scale included 21 items across three dimensions. The Cronbach’s α coefficient was 0.953; split-half reliability, test-retest reliability, and the scale level content validity index were 0.957, 0.885, and 0.926 respectively. The correlation coefficients between each dimension and the total score of the scale and SDM-9 scores were 0.590–0.650 (P < 0.05). Exploratory factor analysis extracted three common factors; the Kaiser-Meyer-Olkin value was 0.974 and the Bartlett’s sphericity test χ ² value was 5652.33 (P < 0.001); the cumulative variance explained was 60.920%. The fit indices of the scale model tested in the confirmatory factor analysis were as follows: χ ² /df = 1.059, RMR = 0.033, GFI = 0.936, CFI = 0.968, TLI = 0.964, NFI = 0.641, RMSEA = 0.015. Confirmatory factor analysis revealed that the scale’s factor structure was stable. Conclusions This instrument is a reliable and valid measurement tool for assessing adult patients’ level of participation in decision-making regarding treatment for malocclusion.