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A comparison of severity of illness scoring systems for intensive care unit patients: Results of a multicenter, multinational study

Castella, Xavier MD; Artigas, Antoni MD; Bion, Julian MBBS MRCP, FRCA, MD; Kari, Aarno MD

Clinical Investigation

Objective To compare the performance of three severity of illness scoring systems used commonly for intensive care unit (ICU) patients in a large international data set. The systems analyzed were versions II and III of the Acute Physiology and Chronic Health Evaluation (APACHE) system, versions I and II of the Simplified Acute Physiology Score (SAPS), and versions I and II of the Mortality Probability Model (MPM), computed at admission and after 24 hrs in the ICU.

Design A multicenter, multinational cohort study.

Setting One hundred thirty-seven ICUs in 12 European and North American countries.

Patients During a 3-month period, 14,745 patients were consecutively admitted to 137 ICUs enrolled in the study.

Interventions Collection of information necessary to compute the APACHE II and APACHE III scores, SAPS I and SAPS II, and MPM I and MPM II scores. Patients were followed until hospital discharge. Statistical comparison, including indices of calibration (goodness-of-fit) and discrimination (area under the receiver operating characteristic curve).

Measurements and Main Results Despite having acceptable receiver operating characteristic areas, the older versions of the systems analyzed (APACHE II, SAPS, and MPM I computed at admission-MPM I computed after 24 hrs in the ICU) demonstrated poor calibration for the whole database. The new versions of the systems (SAPS II and MPM II) were superior to their older counterparts. This superiority is reflected by larger receiver operating characteristic areas and better fit. The APACHE III system improved its receiver operating characteristic area compared with the APACHE II system, which showed the best fit of the old systems analyzed.

Conclusions The new versions of the severity systems analyzed (APACHE III, SAPS II, MPM II) perform better than their older counterparts (APACHE II, SAPS I, and MPM I). APACHE II, SAPS II, and MPM II show good discrimination and calibration in this international database.

(Crit Care Med 1995; 23:1327-1335)

The European/North American Severity Study Group*; From the Critical Care Department (Dr. Castella), Manresa General Hospital, Barcelona, Spain; the Intensive Care Medicine Service (Dr. Artigas), Hospital de Sabadell, Barcelona, Spain; the Department of Anesthesia and Intensive Care (Dr. Bion), the University of Birmingham, Queen Elizabeth Hospital, Birmingham, UK; and the Department of Intensive Care (Dr. Kari), Kuopio University Hospital, Kuopio, Finland.

This study was supported, in part, by departmental funding from the participating institutions.

*Participants in the European/North American Severity Study are listed in Appendix 1.

© Williams & Wilkins 1995. All Rights Reserved.