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. 2025 Nov 1;282(5):670-677.
doi: 10.1097/SLA.0000000000006877. Epub 2025 Aug 12.

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

Fariba Abbassi  1   2   3 , Matthias Pfister  3   4 , Julia Braun  2 , Eva Angenete  5   6 , Eva Haglind  5   6 , Aron Onerup  7   8 , Margot H M Heijmans  9 , Gerrit D Slooter  9 , Charlotte J L Molenaar  9 , Julio F Fiore Jr  10 , Liane S Feldman  10 , Nicolò Pecorelli  11 , Giovanni Guarneri  11 , Massimo Falconi  11 , Sarkis K Drejian  12   13 , Åsmund A Fretland  12   13   14 , Bjorn Edwin  12   13   14 , Sander Ubels  15 , Gerjon Hannink  16 , Milo A Puhan  2   3 , Pierre-Alain Clavien  1   3   4   17
Affiliations

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

Fariba Abbassi et al. Ann Surg. .

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.

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Conflict of interest statement

P.A.C. developed the Clavien-Dindo classification. P.A.C. and M.A.P. developed the Comprehensive Complication Index (CCI ® ). The remaining authors report no conflicts of interest.

References

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    1. Slankamenac K, Graf R, Barkun J, et al. The comprehensive complication index: a novel continuous scale to measure surgical morbidity. Ann Surg. 2013;258:1–7.
    1. Clavien PA, Vetter D, Staiger RD, et al. The Comprehensive Complication Index (CCI ® (R)): added value and clinical perspectives 3 years “down the line”. Ann Surg. 2017;265:1045–1050.
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    1. Clavien PA, Barkun J, de Oliveira ML, et al. The Clavien-Dindo classification of surgical complications: five-year experience. Ann Surg. 2009;250:187–196.

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