Reliability and validity of the Taiwan Chinese version of the Lower Extremity Functional Scale

Background/purpose: The Lower Extremity Functional Scale (LEFS) is a region-specific functional outcome measure designed for patients with lower extremity musculoskeletal dysfunction. In this study, a Taiwan Chinese version was adapted and its validity and reliability were tested.

Methods: The LEFS questionnaire was adapted and tested in 159 patients with lower extremity disorders from two university hospitals. The Cronbach α-coefficient value was calculated for internal consistency. Intraclass correlation coefficient (ICC), Bland-Altman plot, and minimal detectable change (MDC) were used for evaluating the test-retest reliability and agreement in 40 patients followed up within 7 days. Construct and convergent/divergent validity were examined by principal component analysis and correlation was examined with the Medical Outcomes Study Short Form-36 (SF-36) questionnaire.

Results: The internal consistency and test-retest reliability of the adapted LEFS questionnaire were satisfactory [Cronbach α: 0.98; ICC(2,1), 0.97]. The Bland-Altman plot of the two tests showed a relatively consistent distribution, with limits of agreement in the range of -9.32 to 13.02. The MDC at 90% confidence interval was 9.6. One-factor model was confirmed by principal component analysis. Also, there was a moderate association between the LEFS and the physical component scores and several subscales of SF-36, but not with the mental component scores.

Conclusion: The Taiwan Chinese version of the LEFS questionnaire is a valid and reliable measure of health status for patients with lower extremity disorders.