Development and Validation of a Disease-Specific Patient-Reported Outcome Measure for Adult Spinal Deformity: Japanese Society for Spine Surgery and Related Research Adult Spinal Deformity Evaluation Questionnaire

Abstract

Introduction: Adult spinal deformity (ASD) is a multidimensional condition that substantially impairs health-related quality of life. Existing patient-reported outcome measures (PROMs), including the Scoliosis Research Society (SRS) -22r and the Oswestry Disability Index (ODI), do not fully capture ASD-specific symptoms such as fatigue, deformity-related visceral complaints, and stiffness-related functional limitations. We developed and validated a novel ASD-specific instrument, the Japanese Society for Spine Surgery and Related Research (JSSR) -ASD Evaluation Questionnaire (JASDEQ).

Methods: In this multicenter prospective study, 100 patients with ASD and 46 asymptomatic controls were enrolled. Item reduction was performed using predefined criteria including test–retest reliability, responsiveness, inter-item correlations, and overlap with the SRS-22r domains. Internal consistency was assessed using Cronbach' s α. Exploratory factor analysis with parallel analysis was used to determine dimensionality. Construct validity was evaluated using Spearman correlations with the SRS-22r, ODI, EuroQol 5 dimensions (EQ-5D), and external anchors at 6 months. Responsiveness was assessed using standardized response mean (SRM). Incremental validity beyond the SRS-22r was examined using hierarchical regression models.

Results: After item refinement, JASDEQ demonstrated strong internal consistency (α = 0.87-0.89) and acceptable reproducibility. Parallel analysis supported a three-factor structure: Symptom Burden, Activity Limitation, and Spinal Stiffness. All domains discriminated patients with ASD from controls (p < 0.001). Postoperative improvement was significant across domains, with large effect sizes (SRM ≥ 0.8). No floor or ceiling effects were observed at the domain or total score level. JASDEQ subtotal scores correlated strongly with global disability, symptom severity, and EQ-5D. In regression analyses, JASDEQ provided significant incremental explanatory value for EQ-5D in addition to the SRS-22r alone (ΔR² = 0.08, p < 0.001).

Conclusions: JASDEQ is a reliable, responsive, and clinically meaningful ASD-specific PROM. By incorporating deformity-related symptoms and spinal stiffness, it provides incremental validity beyond existing instruments and offers a comprehensive assessment of disability in ASD.