PREDICTING OUTCOME IN THE INTENSIVE-CARE UNIT USING SCORING SYSTEMS -IS NEW BETTER - A COMPARISON OF SAPS AND SAPS-II IN A COHORT OF 1,393PATIENTS

OBJECTIVES. This study sought to compare the performance of the old an d new versions of the Simplified Acute Physiology Score, SAPS and SAPS II, in classifying patients according to the risk of hospital mortali ty. METHODS. TO compare the performance of the two systems, measures o f association between the scores and observed mortality were adopted, together with discrimination (area under the Receiver Operating Charac teristics curve) and calibration (goodness-of-fit statistics) estimate s. Subjects were 1,393 eligible patients recruited during 1 month in 1 994. The outcome measure was vital status at hospital discharge. RESUL TS. SAPS II was associated more strongly with hospital mortality than the earlier version. SAPS II: also had better discrimination ability t han SAPS (area under Receiver Operating Characteristics curve 0.80 ver sus 0.74) and predicted an overall number of deaths (416.5) closer to the observed figure (475) than SAPS (267.7). Conversely, neither SAPS nor SAPS II fitted our data. Both P values derived from goodness-of-fi t statistics were lower than 0.05. CONCLUSIONS. SAPS II offers a real improvement compared with SAPS in its ability to explain hospital mort ality, but its standard parameters do not fit our data from Italy. The role and impact of potential determinants of this lack of fit, such a s random errors and confounders related to casemix and/or quality of c are should be clarified before this scoring system be used outside for mal research projects. Special caution is suggested when SAPS II is ad opted to predict mortality to compare intensive care unit performance across different countries and systems of care.