Toward the rational use of standardized infection ratios to benchmark surgical site infections.

Background: The National Healthcare Safety Network transitioned from surgical site infection (SSI) rates to the standardized infection ratio (SIR) calculated by statistical models that included perioperative factors (surgical approach and surgery duration). Rationally, however, only patient-related variables should be included in the SIR model.

Methods: Logistic regression was performed to predict expected SSI rate in 2 models that included or excluded perioperative factors.