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

Abstract

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