Objective: To compare, in subjects undergoing general surgery, two measures of intrinsic patients risk for nosocomial infection: the Study on the Efficacy of Nosocomial Infection Control (SENIC) index and the National Nosocomial Infection Surveillance (NNIS) System index.
Design: Prospective cohort study, with follow-up for 1 month after hospital discharge.
Setting: The general surgery service of a tertiary hospital.
Main outcome measure: Surgical-site infection.
Patients: 1,483 subjects aged 10 to 92 years.
Results: During follow-up, 155 patients developed nosocomial infection, yielding a cumulative incidence of 10.5%. The NNIS index showed a linear trend with both crude and adjusted (for SENIC index) rates of surgical-wound infection. The SENIC index did not exhibit any linear trend with adjusted (for NNIS index) rates of surgical-wound infection. To delineate whether the SENIC index added explanatory information to the NNIS index (or vice versa), we regressed each variable on the other. Logistic regression analyses confirmed the results of stratified analysis: residuals of the NNIS index added discriminating ability to the SENIC index, whereas residuals of the SENIC index did not improve the predictive power of the NNIS index.
Conclusions: The NNIS index had a better ability than the SENIC index for discriminating and predicting risk of surgical-wound infection.