Translation, validity, and reliability of the Thai de Morton Mobility Index in patients following hip surgery.

Objective: This study aimed to translate the de Morton Mobility Index (DEMMI) into Thai and assess its measurement properties.

Methods: The de Morton Mobility Index (DEMMI) was translated into Thai using a cross-cultural translation method. A cross-sectional study was conducted in four public hospitals in Thailand between January and March 2023. A total of 260 patients were recruited from outpatient clinics. Convergent and known-group validity were evaluated through hypothesis testing. Construct validity was examined using confirmatory factor analysis. Reliability was assessed using Cronbach's α coefficient. We also employed the Rasch analysis to validate validity and person reliability.

Results: Content validity was high (S-CVI = 0.96, I-CVI range: 0.80-1.00). Strong convergent validity was observed, with a significant correlation ( = 0.761, < 0.001) between the Thai DEMMI and the Parker Mobility Scale (PMS). Known-group validity was evident, demonstrating differences in scores across various patient groups. A confirmatory factor analysis supported the hypothesized factor structure of the Thai DEMMI with good fit indices: ( = 4) = 5.101, = 0.2771; / = 1.275, RMSEA = 0.033; CFI = 0.998; TLI = 0.995; SRMR = 0.016. The Thai DEMMI exhibited high internal consistency (Cronbach's α = 0.88). Rasch analysis revealed good person reliability (0.91) and acceptable information-weighted fit means square statistic (0.73-1.06). However, most items showed good fit based on the outlier-sensitive fit means square statistics (Outfit MNSQ), one exhibited a high Outfit MNSQ value of 29.94, suggesting a potential misfit.

Conclusion: This study demonstrated the acceptable validity and reliability of the Thai DEMMI. Further evaluation of its responsiveness to change is still recommended.