Risk adjustment for surgical site infection after median sternotomy in children.

Objective: To determine whether the National Nosocomial Infections Surveillance (NNIS) System risk index adequately stratified a population of pediatric patients undergoing cardiac surgery according to the risk of developing surgical site infection (SSI).
Design: A retrospective, case-control study.
Setting: An urban tertiary care children's hospital.
Patients: Patients who had a median sternotomy performed between January 1, 1995, and December 31, 2003, were eligible for inclusion in the study. For all case patients, medical records were reviewed to verify that all patients met the case definition for SSI. Control subjects were chosen randomly from among all patients who underwent median sternotomy during the study period who did not develop SSI.
Results: Thirty-eight patients with SSI and 172 patients without SSI were included. One hundred six patients (50%) were male. The median patient age was 4 months. The sensitivity of the NNIS risk index with cutoff scores of 0 to 1 and 2 to 3 was 20%. The distribution of patients with SSI for an NNIS risk index score of 0 was 0%; for a score of 1, 80%; for a score of 2, 20%; and for a score of 3, 0%. The distribution of patients without SSI for a scores of 0 was 4%; for a score of 1, 87%; for a score of 2, 9%; and for a score of 3, 0%. The area under the receiver-operating characteristic curve (AUC) of the original NNIS risk index was 0.57. The modified risk indices did not perform significantly better, with an AUC range of 0.58 to 0.73.
Conclusions: The NNIS risk index did not adequately stratify pediatric patients undergoing median sternotomy according to their risk of developing an SSI. Various modifications to the risk index yielded only slightly higher AUC values.