Severity scores in respiratory intensive care: APACHE II predicted mortality better than SAPS II

Background: In recent years several scoring systems have been developed to describe the severity of illness, to establish the individual prognosis, and to group adult ICU patients by predicted risk of mortality. In addition, these scores can be used to measure and/or compare the quality of care in different ICUs. We compared the mortality predictions of the Acute Physiology and Chronic Health Evaluation (APACHE II) score and a new Simplified Acute Physiology Score (SAPS II) in patients with respiratory disease who require intensive care. Patients & methods: We prospectively studied all 306 admissions from January 1, 1992 through December 31, 1994. McNemar and Hosmer-Lemeshow tests, and receiver operating characteristic (ROC) curves were used to describe and analyze our data. Results: The average APACHE II score was 17.5 (SD 6.0), corresponding to a mean predicted death rate of 24.9% (SD 17.2%) as compared to an observed overall RICU mortality rate of 21.6%. The average SAPS II score was 39.1 (SD 11.1) corresponding to a mean predicted death rate of 26.0% (SD 18.4%). The ratio between the actual and predicted hospital mortality was 86% for APACHE II and 83% for SAPS II. Survivors had a significantly lower predicted risk of death than nonsurvivors (p < 0.0001) with both indices, and a higher Glasgow coma scale score (p < 0.0001). The ROC-curve analysis suggested the superior predictive ability of APACHE II in our patients. Area under the APACHE II ROC curve was 80.88% (standard error [SE] 2.89%), significantly larger (p < 0.01) than that found for SAPS II (73.52%, SE 3.61%). Conclusions: The APACHE II score was a good predictor of hospital outcome and better than SAPS II in our population.