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

ABSTRACT

BACKGROUND: 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. AIM: 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. DESIGN: Prospective observational study. SETTING: The setting was outpatient rehabilitation hospital. POPULATION Two hundred and five patients with chronic LBP. METHODS: 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. RESULTS: 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). CONCLUSIONS: 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. CLINICAL REHABILITATION IMPACT 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.