Responsiveness and minimal important change of the Pain Catastrophizing Scale in people with chronic low back pain undergoing multidisciplinary rehabilitation.

Abstract

The Pain Catastrophizing Scale (PCS), a widely used tool to assess catastrophizing related to spinal disorders, shows valid psychometric properties in general but the minimal important change (MIC) is still not determined. The aim of this study was to assess responsiveness and MIC of the PCS in individuals with chronic low back pain (LBP) undergoing multidisciplinary rehabilitation. Prospective observational study. The setting was outpatient rehabilitation hospital. Two hundred and five patients with chronic LBP. Before and after an 8-week multidisciplinary rehabilitation program, 205 patients completed the Italian version of the PCS (PCS-I). We calculated the PCS-I responsiveness by distribution-based methods (effect size [ES], standardized response mean [SRM], and minimum detectable change [MDC]) and anchor-based methods [receiver operating characteristic (ROC) curves]. After the program, participants completed a 7-point global perceived effect scale (GPE), based on which they were classified as "improved" vs. "stable." ROC curves computed the best cut-off level (taken as the MIC) between the two groups. ROC analysis was also performed on subgroups according to patients' baseline PCS scores. ES, SRM and MDC were 0.71, 0.67 and 7.73, respectively. ROC analysis yielded an MIC of 8 points (95% confidence interval [CI]: 6-10; area under the curve [AUC]: 0.88). ROC analysis of the PCS subgroups confirmed an MIC of 8 points (95%CI: 6-10) for no/low catastrophizers (score <30, N.=159; AUC: 0.90) and indicated an MIC of 11 points (95%CI: 8-14) for catastrophizers (score >30, N.=33; AUC: 0.84). The PCS-I showed good ability to detect patient-perceived clinical changes in chronic LBP postrehabilitation. The MIC values we determined provide a benchmark for assessing individual improvement in this clinical context. The present study calculated - in a sample of people with chronic LBP - the responsiveness and MIC of the PCS. These values increase confidence in interpreting score changes, enhancing their meaningfulness for both research and clinical contexts.