Beyond P Values : Novel Minimal Important Difference of the Comprehensive Complication Index That Reflects a Meaningful Outcome for Patients Undergoing Major Abdominal Surgery

Abstract

Objective: To estimate the minimal important difference (MID) of the Comprehensive Complication Index (CCI ® ) in patients undergoing abdominal surgery.

Background: The CCI ® is a validated metric that quantifies cumulative surgical morbidity. While the CCI ® is a sensitive endpoint to detect treatment effects, a statistically significant effect does not necessarily translate into clinical relevance. Relevant differences from the patients' perspective are best captured by the MID.

Methods: Individual patient data were extracted from surgical studies reporting CCI ® at 30 days and using patient-reported outcome measures with established MIDs at baseline and 30 days. To determine the MID for the CCI ® , we used an anchor-based approach as recommended by methods guidelines. A patient-reported outcome measure was selected as an anchor only if the Spearman correlation coefficient between its change in score (baseline to 30 days postoperative) and the CCI ® was ≥|0.30|. We used linear regression to estimate the MID of the CCI ® across different anchors, and triangulation to determine a single MID.

Results: Data were extracted from 3 published randomized controlled trials and 1 prospective observational study (n = 1583 patients) in major abdominal surgery. In colorectal surgery cohorts, 2 subscores of the Short Form-36, 2 subscores of the Multidimensional Fatigue Inventory-20, the EuroQol-5-Dimension Index Score, and the EuroQol Visual Analog Scale showed a correlation with the CCI ® of ≥|0.30|. This resulted in MID estimates for the CCI ® ranging from 6.1 to 22.2. In hepato-pancreato-biliary surgery, 1 subscore of the Short Form-36, and 2 subscores of the Patient Reported Outcome Measure Information System-29 questionnaire qualified as anchors providing MID estimates ranging from 6.2 to 13.8.

Conclusions: We propose a mean difference of 12 points in the CCI ® between treatment groups as a relevant difference in patients undergoing abdominal surgery. This MID provides an important foundation for sample size calculations and interpretation of randomized controlled trials and large real-world observational studies.

Keywords: MID; anchor-based approach; clinical significance; comprehensive complication index; minimal important difference; outcome reporting; patient reported outcome measures.