Construct Validity and Reliability of the Comprehensive Complication Index as a Morbidity Outcome Measure in Pancreatic Surgery

Objective: To assess the reliability and construct validity of the CCI®️ following pancreatic surgery. Summary background data: The Comprehensive Complication Index (CCI®️) is the only validated metric that quantifies cumulative morbidity, with a continuous score ranging from 0 (no complications) to 100 (death). Methods: To address construct validity, we assessed patients undergoing elective pancreatic surgery for any disease at five Italian centers enrolled in a randomized controlled trial (NCT04438447) and a prospective cohort study (NCT04431076). The severity of 90-day complications was assessed using the CCI®️. We tested 10 a priori construct validity hypotheses through linear regression. Regression coefficients represented the between-group mean difference in CCI®️, with an effect size ≥0.2 considered potentially meaningful. Validity was deemed adequate if >75% of the hypotheses were supported. To address reliability, three independent raters among six centers assessed the CCI®️ from 100 anonymous case vignettes to evaluate inter-rater and inter-center reliability through intraclass correlation coefficient (ICC) and standard error of measurement (SEM). Results: 797 patients were included (66±11 y, 50% female, 60% malignancy). The construct validity was supported by data, with 9/10 a priori hypotheses confirmed (90%). The CCI®️ showed excellent inter-rater (ICC=0.96, 95%CI: 0.95-0.97), high inter-center reliability (ICC >0.75 in each center), with a SEM ranging from 2.73 to 6.38. Conclusions: This study supports CCI®️as a valid and reliable measure of morbidity after pancreatic surgery, supporting its use in both clinical practice and comparative effectiveness research.