The Lower Extremity Functional Scale (LEFS): scale development, measurement properties, and clinical application. North American Orthopaedic Rehabilitation Research Network.

TLDR

The study aimed to evaluate the reliability, construct validity, and sensitivity to change of the Lower Extremity Functional Scale (LEFS) in patients with lower‑extremity musculoskeletal dysfunction. The authors administered the LEFS and SF‑36 to 107 patients at baseline, 24–48 h, and weekly for four weeks, then used intraclass correlation coefficients, Pearson correlations, ANOVA, and Spearman rank‑order correlations to assess test‑retest reliability, construct validity, and responsiveness. The LEFS demonstrated excellent test‑retest reliability (ICC = .94), strong correlations with SF‑36 physical function (r = .80) and component scores (r = .64), a higher prognostic‑rating correlation than SF‑36, a minimal detectable change and clinically important difference of 9 points, and superior sensitivity to change, confirming its reliability, validity, and clinical utility.

Abstract

The purpose of this study was to assess the reliability, construct validity, and sensitivity to change of the Lower Extremity Functional Scale (LEFS).The LEFS was administered to 107 patients with lower-extremity musculoskeletal dysfunction referred to 12 outpatient physical therapy clinics.The LEFS was administered during the initial assessment, 24 to 48 hours following the initial assessment, and then at weekly intervals for 4 weeks. The SF-36 (acute version) was administered during the initial assessment and at weekly intervals. A type 2,1 intraclass correlation coefficient was used to estimate test-retest reliability. Pearson correlations and one-way analyses of variance were used to examine construct validity. Spearman rank-order correlation coefficients were used to examine the relationship between an independent prognostic rating of change for each patient and change in the LEFS and SF-36 scores.Test-retest reliability of the LEFS scores was excellent (R = .94 [95% lower limit confidence interval (CI) = .89]). Correlations between the LEFS and the SF-36 physical function subscale and physical component score were r=.80 (95% lower limit CI = .73) and r = .64 (95% lower limit CI = .54), respectively. There was a higher correlation between the prognostic rating of change and the LEFS than between the prognostic rating of change and the SF-36 physical function score. The potential error associated with a score on the LEFS at a given point in time is +/-5.3 scale points (90% CI), the minimal detectable change is 9 scale points (90% CI), and the minimal clinically important difference is 9 scale points (90% CI).The LEFS is reliable, and construct validity was supported by comparison with the SF-36. The sensitivity to change of the LEFS was superior to that of the SF-36 in this population. The LEFS is efficient to administer and score and is applicable for research purposes and clinical decision making for individual patients.