Chronic pain after surgery: time for standardization? A framework to establish core risk factor and outcome domains for epidemiological studies.

INTRODUCTION AND
OBJECTIVES: Many studies have reported putative factors for the development of chronic pain after surgery. However, advances in knowledge about the etiology and prognosis of chronic postsurgical pain (CPSP) could be gained by improving methodology within studies of surgical pain. The purpose of this study was to review predictive factors and to propose core risk factor and outcome domains for inclusion in future epidemiological studies investigating CPSP.
METHODS: Using the Initiative on Methods, Measurement, and Pain Assessment in Clinical Trials as a framework we reviewed risk factor and outcome domains, methodological issues and standardized measurement tools based on findings from narrative and systematic reviews, primary clinical and epidemiological studies and published guidelines for chronic pain clinical trials.
RESULTS: Five "core" risk factor domains (demographic, pain, clinical, surgery-related, and psychological) and 4 outcome domains (pain, physical functioning, psychological functioning, and global ratings of outcome) were identified. Important methodological issues, related to the definition and timing of follow-up to assess transition from acute to chronic pain are discussed. We also propose the use of validated, standardized measurement tools to capture risk factor and outcome domains at multiple time points. DISCUSSION: There is potential to advance the field of CPSP research by striving for consensus among pain experts; this would advance current evidence by improving our ability to compare findings from different studies and would facilitate the aggregation of surgical cohort datasets to allow international comparisons. We propose these findings as a starting point to build a comprehensive framework for epidemiological studies investigating chronic pain after surgery.