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

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

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.

Content validity was high (S-CVI = 0.96, I-CVI range: 0.80-1.00). Strong convergent validity was observed, with a significant correlation (r = 0.761, P < 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: χ ² (df = 4) = 5.101, P = 0.2771; χ ²/df = 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.

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