Validation of a self-report measure for diagnostic screening and assessment in complex regional pain syndrome

Introduction: Complex regional pain syndrome (CRPS) is an orphan condition with no interventions proven effective in large-scale clinical trials. In-person clinical evaluations are required to make a CRPS diagnosis and determine study eligibility, making recruitment for CRPS trials challenging. Objectives: We developed and validated a self-report measure of CRPS symptoms suitable for remote administration. Methods: We evaluated diagnostic accuracy of a self-report version of the CRPS Severity Score (CSS-SR) and assessed its validity relative to the original clinician-completed CSS (CSS-Clinician) in two samples: 112 postsurgical patients with total knee arthroplasty and 80 patients with CRPS and non-CRPS limb pain attending a chronic pain clinic. All patients completed the CSS-SR and underwent a semi-structured history and physical examination from which the CSS-Clinician was scored and a criterion-based Budapest CRPS diagnosis was determined. Results: There was good to excellent correspondence (intraclass correlations [ICCs]) between CSS-Clinician and CSS-SR total scores (postsurgical sample: ICCs = 0.86-0.92; pain clinic sample: ICC = 0.76). In the postsurgical sample, the 2 measures displayed good agreement regarding changes in CRPS features across 2 assessments 4 months apart (ICC = 0.84). The CSS-SR exhibited high diagnostic accuracy in receiver operating characteristic analyses (area under the curve = 0.84–0.94). In the pain clinic sample, a CSS-SR cutoff of ≥8 had a 79% probability of correctly predicting a Budapest CRPS diagnosis after full evaluation (sensitivity = 0.79, specificity = 0.79). Conclusion: The CSS-SR appears valid as a self-report measure of CRPS status and displays good accuracy as a remote diagnostic screening tool.