Lumbar Spinal Stenosis–Specific Symptom Scale: Validity and Responsiveness

STUDY DESIGN. Cross-sectional study. OBJECTIVES. To test the validity and responsiveness of the lumbar spinal stenosis (LSS)–specific symptom scale (FLS-25 [Fukushima LSS Scale 25]). SUMMARY OF BACKGROUND DATA. The FLS-25, a self-administered questionnaire designed to comprehensively cover various symptoms of LSS, has been developed to address the need to measure symptoms specific to this disorder. METHODS. One hundred sixty-seven patients with confirmed LSS who required conservative therapy were asked to complete a questionnaire including questions regarding walking capacity and the FLS-25. These patients also underwent a lumbar extension test and a walking stress test, which are stress tests designed to objectively evaluate LSS symptoms, to measure standing time, walking distance, and walking time. Relationship between the FLS-25 scores and these external standards was analyzed to evaluate the criterion validity of the FLS-25. The patients underwent the same evaluations after 8 weeks of conservative therapy. The relationship between changes from baseline to week 8 in FLS-25 scores and changes in the 3 external standards was analyzed to evaluate the responsiveness of the FLS-25. RESULTS. The distribution of FLS-25 scores among patients was symmetric, and there were no ceiling or floor effects. FLS-25 scores increased as self-reported walking capacity decreased (P = 0.006). The mean standing time in the lumbar extension test was 165 (SD = 109) seconds, and FLS-25 scores increased as standing time decreased (P = 0.003). In the walking stress test, mean walking distance and mean walking time were 213 (SD = 154) m and 236 (SD = 114) seconds. FLS-25 scores increased as walking distance (P = 0.002) and walking time (P = 0.054) decreased. Changes from baseline to week 8 in FLS-25 scores correlated with changes in the stress test standing time (P = 0.014), walking distance (P < 0.001), and walking time (P < 0.001). CONCLUSION. The criterion validity and responsiveness of the FLS-25 were confirmed. The use of FLS-25 in clinical and investigational settings is warranted to monitor patients and evaluate therapeutic efficacy. Level of Evidence: 3