External validation of IASP diagnostic criteria for complex regional pain syndrome and proposed research diagnostic criteria

Recent work in our research consortium has raised internal validity concern s regarding the current IASP criteria for Complex Regional Pain Syndrome (C RPS), suggesting problems with inadequate sensitivity and specificity. The current study explored the external validity of these IASP criteria for CRP S, A standardized evaluation of signs and symptoms of CRPS was conducted by study physicians in 117 patients meeting IASP criteria for CRPS, and 43 pa tients experiencing neuropathic pain with established non-CRPS etiology (e. g. diabetic neuropathy, post-herpetic neuralgia), Multiple discriminant fun ction analyses were used to test the ability of the IASP diagnostic criteri a and decision rules, as well as proposed research modifications of these c riteria, to discriminate between CRPS patients and those experiencing non-C RPS neuropathic pain. Current IASP criteria and decision rules (e.g, signs or symptoms of edema, or color changes or sweating changes satisfy criterio n 3) discriminated significantly between groups (P < 0.001). However, altho ugh sensitivity was quite high (0.98), specificity was poor (0.36), and a p ositive diagnosis of CRPS was likely to be correct in as few as 40% of case s. Empirically-based research modifications to the criteria, which are more comprehensive and require presence of signs and symptoms, were also tested . These modified criteria were also able to discriminate significantly, bet ween the CRPS and non-CRPS groups (P < 0.001). A decision rule, requiring a t least two sign categories and four symptom categories to be positive opti mized diagnostic efficiency, with a diagnosis of CRPS likely to be accurate in up to 84% of cases, and a diagnosis of non-CRPS neuropathic pain likely to be accurate in up to 88% of cases. These results indicate that the curr ent IASP criteria for CRPS have inadequate specificity and are likely to le ad to overdiagnosis. Proposed modifications to these criteria substantially improve their external validity and merit further evaluation. (C) 1999 Int ernational Association for the Study of Pain. Published by Elsevier Science B.V.