Influence of the severity of illness measured by the simplified acute physiology score (SAPS) on occurrence of nosocomial infections in ICU patients

To evaluate the ability of the Simplified Acute Physiology Score (SAPS) to predict the occurrence of hospital-acquired infections in intensive care unit (ICU) patients, we conducted a cohort study in an eight-bed combined ICU. From January 1991 to December 1992, 690 patients were admitted in the ICU and 656 stayed at least -C8 h. Patients' severity of illness was estimated within the first 24 h of the ICU stay using the SAPS. Nosocomial infection rates were compared between the high SAPS group (>10 points) and the low SAPS group (less than or equal to 10 points), with the cut-off point chosen according to a ROC curve. One hundred (15.2%) patients developed hospital-acquired infections during their ICU stay. The mean SAPS of infected patients was significantly higher than the mean SAPS of noninfected patients (15.4 +/- 1.3 vs. 12.0 +/- 5.9 points, P<0.0001). Significantly more infections occurred in the patients with a SAPS >10 points (20.9% vs. 5.1%, P<0.0001). Sensitivity, specificity, positive and negative predictive values for a SAPS >10 points were 88, 40, 21, and 95%, respectively. Our results suggest that 95% of patients at low risk for developing hospital acquired infections could be identified on admission with the use of severity scoring systems such as SAPS less than or equal to 10 points.