Cross-cultural adaptation and the evaluation of psychometric properties of the Sinhala version of the general rehabilitation adherence scale (GRAS-Sin).

BACKGROUND

Physiotherapy adherence can be defined as an active, voluntary patient involvement in a mutually agreed-upon course of action to achieve a desired preventive or therapeutic outcomes. Nonadherence may result in increased healthcare costs and poor recovery. Therefore, it is crucial to measure physiotherapy adherence to eliminate obstacles and promote adherence. No validated tool exists to measure physiotherapy adherence among Sinhala-speaking patients in Sri Lanka.

METHODS

This study aimed to develop a Sinhala version of the General Rehabilitation Adherence Scale (GRAS-Sin). During the first phase, the original version of the GRAS was translated and culturally adapted to the Sinhala language. In the second phase, a cross-sectional survey was conducted among 200 patients who sought physiotherapy treatment for musculoskeletal issues at the National Hospital, Kandy and the Teaching Hospital, Peradeniya, Sri Lanka, to evaluate its psychometric properties. The pre-final version of the questionnaire developed in the first phase was used in the second phase.

RESULTS

The majority of the respondents were female (71.5%). Most patients (54.5%) showed a high level (20-24 total scores) of physiotherapy adherence. There was an acceptable level of internal consistency (Cronbach's alpha = 0.82) and test-retest reliability (intraclass correlation coefficient = 0.907, p < 0.05). The content validity index of the scale was 0.89. The sampling adequacy was satisfactory (KMO = 0.755, Bartlett's test p < 0.05). Construct validity was measured by exploratory factor analysis, which revealed a 2-factor model with a 73.4% variance. The incremental fit indices, i.e., the normed fit index, comparative fit index and Tucker-Lewis index, were reported to be > 0.95, whereas the absolute fit index of the root mean square of the approximation error was 0.065. These values indicated a good model fit. No floor and 27% ceiling effects were found. There was a significant (X = 17.46, p = 0.001) relationship between physiotherapy adherence and gender, whereas age, employment status, educational level, and economic status were not significant.

CONCLUSION

The GRAS-Sin questionnaire is a valid and reliable tool for assessing physiotherapy adherence among Sinhala-speaking patients in Sri Lanka. However, its ceiling effect may limit differentiation at higher adherence levels. Further studies are required to address the limitations of the ceiling effect in the present study.