The performance and customization of SAPS 3 admission score in a Thai medical intensive care unit

Abstract

The aim of this study was to evaluate the performance of Simplified Acute Physiology Score 3 (SAPS 3) admission scores, both the original and a customized version, in mixed medical critically ill patients. A prospective cohort study was conducted over a 2-year period in the medical intensive care unit (MICU) of a tertiary referral university teaching hospital in Thailand. The probability of hospital mortality of the original SAPS 3 was calculated using the general and customized Australasia version (SAPS 3-AUS). The patients were randomly divided into equal calibration and validation groups for customization. A total of 1,873 patients were enrolled. The hospital mortality rate was 28.6%. The general equation of SAPS 3 had excellent discrimination with an area under the receiver operating characteristic curve of 0.933, but poor calibration with the Hosmer-Lemeshow goodness-of-fit H = 106.7 and C = 101.2 (P < 0.001), and it overestimated mortality with a standardized mortality ratio of 0.86 (95% confidence interval, 0.79-0.93). The calibration of SAPS 3-AUS was also poor. The customized SAPS 3 showed a good calibration of all patients in the validation group (H = 14, P = 0.17 and C = 11.3, P = 0.33) and all subgroups according to main diagnosis, age, gender and co-morbidities. The SAPS 3 provided excellent discrimination but poor calibration in our MICU. A first level customization of the SAPS 3 improved the calibration and could be used to predict mortality and quality assessment in our ICU or other ICUs with a similar case mix.