An Iranian Version of the Fukushima Lumbar Spinal Stenosis Scale (FLS-25): A Validation Study

STUDY DESIGN Cross-sectional study. PURPOSE To translate and validate the Fukushima lumbar spinal stenosis (LSS) scale 25 (FLS-25) for use in Iran. OVERVIEW OF LITERATURE Tools measuring patient-reported outcomes should satisfy certain psychometric properties. METHODS FLS-25 is a self-administered scale for evaluating symptoms of LSS. A forward-backward procedure was applied to translate the questionnaire from English into Persian. A sample of patients with LSS completed the questionnaire at two points in time: once before surgery and once 6 months after the surgery. The Neurogenic Claudication Outcome Score (NCOS) was also used for assessment. The psychometric properties of FLS-25 were evaluated for internal consistency, test-retest and interobserver reliabilities, responsiveness to change, known-group comparison, and convergent validity. RESULTS In all, 131 patients were included in the study. The mean age of the patients was 61.4 (standard deviation, 11.1) years. The Cronbach's alpha coefficient for FLS-25 was 0.89. Test-retest reliability as carried out by the intraclass correlation coefficient was 0.94 (95% confidence interval, 0.95). Interobserver agreement as measured by the kappa statistics also was found to be acceptable (kappa value, 0.88), and validity was found to be satisfactory. The instrument was able to discriminate between the subgroups of patients who differed in symptom severity. The correlation between FLS-25 and NCOS scores was excellent, indicating good convergent validity (r=0.82, p<0.001). The results also indicated that the instrument was responsive to change (p<0.001). CONCLUSIONS The Iranian version of FLS-25 performed well, and the findings suggest that it is a valid measure of symptom severity in LSS patients.