IL1B and complex regional pain syndrome: For patients with increased levels of the interleukin IL-1beta (and the interleukin soluble receptor sIL-1RI) without an increase in the interleukin soluble receptor sIL-1RII and the interleukin 1 receptor antagonist IL-1Ra, IL-1beta levels similarly correlated positively with both CRPS duration and severity (low risk of bias).