Responsiveness and Minimum Important Change of the Oswestry Disability Index in Italian subjects with Symptomatic Lumbar Spondylolisthesis.

BACKGROUND: This study aims to investigate the responsiveness and the minimum important change of the Italian version of the Oswestry Disability Index (ODI-I) in subjects with symptomatic specific low back pain associated to lumbar spondylolisthesis (SPL). MATERIAL AND METHODS: One hundred fifty-one patients with symptomatic SPL completed the ODI-I, a 0–100 Numerical Rating Scale (NRS), and performed the Prone and the Supine Bridge Tests. The global perception of effectiveness was measured with a 7-point Likert scale. Responsiveness was assessed by distribution methods [Minimum Detectable Change (MDC); Effect Size (ES); Standardized Response Mean (SRM)] and anchor-based methods (ROC curves). RESULTS: The MDC was 4.23; the ES was 0.95 and the SRM was 1.25; ROC analysis revealed an area under the curve of 0.76 thus indicating moderate discriminating capacity; the best cut-off point for the dichotomous outcome was 7.5 (sensitivity 90.3% and specificity 56.7%). CONCLUSIONS: The ODI-I proved to be responsive in detecting changes after conservative treatment in subjects with lumbar SPL. LEVEL OF EVIDENCE: II