Validation of the Risk Index Category as a Predictor of Surgical Site Infection in Elective Colorectal Surgery

PURPOSE: The risk index category is a tool to predict and compare surgical site infection rates among surgeons and hospitals. However, the accuracy of the index in colorectal surgery has been questioned because the index was validated in a patient population with lower surgical site infection rates than recently reported in the literature. This study aims to validate the risk index category as a predictor of surgical site infection in a cohort of patients who underwent colorectal operations and were prospectively surveyed for surgical site infection. METHODS: Demographics, preoperative characteristics, and surgical data were obtained from 491 consecutive patients undergoing elective colorectal resections at a colorectal unit from April 2006 to July 2008. Surgical site infections were prospectively collected and stratified according to the Centers for Disease Control and Prevention criteria. Association of variables with surgical site infection was determined by univariate and multivariate analyses. RESULTS: A total of 95 (19.3%) patients developed surgical site infections. The rate of infection increased in each index category, from 13% for category 0 to 27% for category 3. Risk factors for surgical site infection in univariate analysis were as follows: high American Society of Anesthesiologists' scores, obesity, open surgery, and high index categories. Risk index category > or =2 (OR, 2.3; CI, 1.4-3.9; P < .01) was the only independent risk factor associated with infection in multivariate analysis. CONCLUSION: The risk index category is a strong predictor for the development of surgical site infection in colorectal surgery patients when infections are prospectively collected and should be used to stratify patients when reporting infection rates in elective colorectal surgery.