External Validation of the COMI-Hernia Score and Establishing Minimal Important Difference for Assessing Postoperative Quality of Life Following Inguinal Hernia Repair.

Background: Inguinal hernia repair significantly affects patient quality of life and healthcare costs. The systematic assessment of patient-reported outcomes (PROs) emphasizes the importance of valid and responsive measurement tools. Objective: To externally validate the Core Outcome Measure Index for hernia surgery (COMI-Hernia) and determine its Minimal Important Difference (MID) using an anchor-based approach. Methods: Data from 240 patients who underwent inguinal hernia repair between 2018 and 2020 were analyzed (Asklepios Klinik Langen, Germany). The patients completed the COMI-Hernia questionnaire preoperatively and at multiple postoperative intervals (up to 24 months). Reliability, construct validity, and responsiveness were assessed, and MID values were calculated using the Patient Global Impression of Change. Results: The COMI-Hernia assessment showed high internal consistency (Cronbach's alpha = 0.83), strong construct validity [visual analog scale (VAS) correlation r = 0.728], and excellent responsiveness (standardized response mean = 1.26). MID values were established as 0.5 points for pain and 0.7 points for function. The greatest improvement occurred within the first 3 months and remained stable for up to 24 months. MID thresholds were identified as 0.5 points for pain and 0.7 points for function. Conclusions: COMI-Hernia provides a reliable, valid, and responsive assessment of PROs following inguinal hernia surgery. Defined MID values facilitate meaningful interpretations in clinical practice and research. Future studies should investigate the psychosocial variables, sex-specific differences, and long-term outcomes.