The Lower Extremity Functional Scale (LEFS): Scale Development, Measurement Properties, and Clinical Application

BACKGROUND AND PURPOSE: The purpose of this study was to assess the reliability, construct validity, and sensitivity to change of the Lower Extremity Functional Scale (LEFS). SUBJECTS AND METHODS: The LEFS was administered to 107 patients with lower-extremity musculoskeletal dysfunction referred to 12 outpatient physical therapy clinics. METHODS: 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. RESULTS: 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). CONCLUSION AND DISCUSSION: 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.