Mortality prediction in head trauma patients: performance of Glasgow Coma Score and general severity systems

Abstract

Objective: To assess the performance of general severity systems (Acute Physiology and Chronic Health Evaluation [APACHE] II, Simplified Acute Physiology Score [SAPS] II, and Mortality Probability Models [MPM] II) for head trauma patients and to compare these systems with the Glasgow Coma Score, in order to obtain a good estimate of severity of illness and probability of hospital mortality.

Design: Inception cohort.

Setting: Adult medical and surgical intensive care units in 12 European and North American countries.

Patients: Patients (n = 401) who were diagnosed with head trauma (with/without multiple trauma), leading to intensive care unit admission, and who were not brain dead at the time of arrival.

Interventions: Statistical analysis to assess the performance of general severity systems.

Measurements and main results: Vital status at the time of hospital discharge was the outcome measure. Performance of the severity systems (SAPS II, MPM II0 [MPM at admission], MPM II24 [MPM at 24 hrs], and APACHE II) was assessed by evaluating calibration and discrimination. Logistic regression was used to convert the Glasgow Coma Score into a probability of death. The MPM II system (either MPM II0 or MPM 1124) provided an adequate estimation of the mortality experience in patients with head trauma. SAPS II and APACHE II systems did not calibrate well, although they showed high discrimination (area under the receiver operating characteristic curve 0.95 for SAPS II, 0.94 for APACHE II, and 0.90 for MPM II0 and MPM II24). The logistic regression model containing the Glasgow Coma Score as an independent variable and developed in this group of patients was not as well calibrated as MPM II. The discrimination of this model was very high, in the range observed for the APACHE II, SAPS II, and MPM II systems.

Conclusions: The MPM II system performs better than APACHE II, SAPS II, and Glasgow Coma Score for head trauma patients. If our results are supported by other studies, MPM II would be an appropriate tool to assess severity of illness in head trauma patients, with applications to clinical practice and clinical research.