Surgical site infection surveillance and the predictive power of the National Nosocomial Infection Surveillance index as compared with alternative determinants in The Netherlands

Background: Surgical site infection (SSI) surveillance typically includes comparison between observed and expected infection risks. Expected SSI numbers are usually derived from national data by use of the National Nosocomial Infection Surveillance (NNIS) index, developed by the Centers for Disease Control and Prevention. We aimed to estimate the predictive power of alternative SSI determinants to improve estimation of expected numbers. Methods: We considered surveillance data comprising 93,511 surgical procedures, 3494 SSIs, and 11 putative determinants in The Netherlands in 1996 to 2004. Comparable procedures were pooled into 19 groups, and logistic regression backward elimination defined corresponding alternative models. The predictive power of the alternative models and the NNIS index were compared by testing the areas under the receiver operating characteristic curves. Results: For 9 procedure groups, the alternative models predicted SSI better than the NNIS index (P < .05). However, the corresponding expected SSI numbers were marginally affected. Conclusion: Our results do not support replacement of the NNIS index with procedure-specific determinants when comparing observed and expected SSI occurrence in feedback of surveillance results to hospitals.