External validity and responsiveness of lumbar spinal stenosis–specific symptom and QOL scales: A multicenter prospective study

Lumbar spinal stenosis (LSS) impairs function and quality of life, and two LSS-specific patient-reported outcome (PRO) measures—the LSS Symptom and LSS QOL scales—have been developed; however, their external validity and responsiveness across conservative and surgical pathways have not been established. This prospective multicenter validation study enrolled 243 patients who completed both scales with the Japanese Orthopaedic Association Back Pain Evaluation Questionnaire, Zurich Claudication Questionnaire, and Short Form-36 at baseline. Follow-up was conducted at 6 ± 1 months after conservative care or 3 months after surgery and included satisfaction ratings. External validity was examined using Spearman correlations, and responsiveness was evaluated using change scores, standardized response means, and receiver operating characteristic analyses anchored to treatment satisfaction (≥ 4/5 on a 5-point Likert scale) at 6 ± 1 months (conservative care) or 3 months (surgical care) to estimate minimal clinically important differences. Baseline Symptom scores showed moderate to strong correlations with established PROs, and QOL scores demonstrated similar associations. Improvements in both scales correlated with changes in established PROs and satisfaction. Responsiveness was large overall and greatest among surgical patients. The minimal clinically important differences were 4 points for the Symptom scale (AUC = 0.69, 95%CI 0.60–0.77) and 14 points for the QOL scale (AUC = 0.72, 95%CI 0.64–0.79). These findings support the validity and responsiveness of both scales and their complementary use in assessing LSS outcomes.