To compare the test-retest reliability and validity of the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) physical function (PF) subscale and the Lower Extremity Functional Scale (LEFS) in community-dwelling adults with hip osteoarthritis (OA).
One hundred adults with symptomatic hip OA participated in the study. Test-retest reliability was assessed by administering the WOMAC and LEFS at participants' initial visits and after 1 week. Discriminant validity from pain measures was assessed by examining the WOMAC-PF and the LEFS correlations with the PF and bodily pain subscales of the Medical Outcomes Study 36-Item Short-Form Health Survey (SF-36). Convergent validity was assessed by comparing correlations between the WOMAC-PF and LEFS with the gait speed test, step test, and timed stair tests. Intraclass correlation coefficients (ICCs), standard error of measurement, and Pearson correlation coefficients were calculated.
ICC estimates of 0.90 and 0.92 were obtained for the WOMAC-PF and LEFS, respectively. The minimal detectable change scores were 9.1 WOMAC-PF and 9.9 LEFS points. Discriminant validity was evident for the LEFS but not for the WOMAC-PF. The WOMAC-PF and LEFS showed similar levels of convergent validity; however, WOMAC-PF and gait speed showed a relatively low correlation.
The LEFS has good measurement properties--namely test-retest reliability and cross-sectional construct validity--and it could be an alternative to WOMAC-PF.