Test-Retest Reliability and Responsiveness for the Simplified Chinese Lower Extremity Functional Scale in Patients With Lower Extremity Musculoskeletal Injuries

Abstract

Background: The simplified Chinese Lower Extremity Functional Scale (SC-LEFS) is a patient-reported outcome measure specifically developed for Chinese-speaking patients to assess functional status in those with lower extremity musculoskeletal disorders. However, to date, no studies have specifically examined the reliability and responsiveness of the SC-LEFS in nonarthritic musculoskeletal injuries. Purpose: To define the minimal detectable change (MDC) as a measure of test-retest reliability and the substantial clinical benefit (SCB) as a measure of responsiveness for the SC-LEFS in patients with nonarthritic lower extremity musculoskeletal injuries. Study Design: Cohort study (diagnosis); Level of evidence, 3. Methods: Patients aged between 18 and 50 years with a lower extremity musculoskeletal injury who were referred for physical therapy visits completed the SC-LEFS at the initial assessment and at the 4-week follow-up. Patients were classified into “stable,”“improved,” and “not improved” groups based on self-reported changes at the 4-week follow-up. The “stable” group was used to establish the MDC value for test-retest reliability. The “improved” and “not improved” groups were used to determine the SCB value for responsiveness. Results: A total of 763 patients (44.8% women), with a mean age of 32.9 (SD, 9.4) years, were included. Using the “stable” group (n = 40), excellent test-retest reliability was demonstrated with an intraclass correlation coefficient of 0.98 and an MDC of 5.1 points. To evaluate the responsiveness, the “improved” (n = 497) and “not improved” (n = 266) groups were analyzed. Receiver operator characteristic analysis found an SCB value of 9.5 points on the SC-LEFS. This change score could differentiate those “improved” from those “not improved” with a sensitivity of 0.68, specificity of 0.71, and area under the curve of 0.75 (95% CI, 0.71-0.78). Conclusion: This study offers evidence of test-retest reliability and responsiveness with MDC and SCB values for the SC-LEFS in Chinese-speaking patients with nonarthritic lower musculoskeletal extremity injuries. Clinicians should consider 5.1 points as the measurement error and 9.5 points as the threshold for clinically meaningful improvement on the SC-LEFS in patients with lower extremity musculoskeletal injuries over a 4-week treatment period.