BACKGROUND: The primary aim was to investigate the performance of a National Advisory Committee for Aeronautics based predictive model (NACA-BM) for mortality at 14 days and a reference model using motor GCS (GCS-RM). The secondary aim was to compare the models for impaired consciousness of survivors at 14 days (IC-14; GCS ≤ 13).
METHODS: Patients ≥16 years having sustained TBI with an abbreviated injury scale score of head region (HAIS) of >3 were included. Multivariate logistic regression models were used to test models for death and IC-14. The discrimination was assessed using area under the receiver-operating curves (AUROCs); noninferiority margin was -5% between the AUROCs. Calibration was assessed using the Hosmer Lemeshow goodness-of-fit test.
RESULTS: Six hundred and seventy seven patients were included. The median age was 54 (IQR 32-71). The mortality rate was 31.6%; 99 of 438 surviving patients (22.6%) had an IC-14. Discrimination of mortality was 0.835 (95%CI 0.803-0.867) for the NACA-BM and 0.839 (0.807-0.872) for the GCS-RM; the difference of the discriminative ability was -0.4% (-2.3% to +1.7%). Calibration was appropriate for the NACA-BM (χ2 8.42; P = 0. 393) and for the GCS-RM (χ2 3.90; P = 0. 866). Discrimination of IC-14 was 0.757 (0.706-0.808) for the NACA-BM and 0.784 (0.734-0.835) for the GCS-RM; the difference of the discriminative ability was -2.5% (-7.8% to +2.6%). Calibration was appropriate for the NACA-BM (χ2 10.61; P = 0.225) and for the GCS-RM (χ2 6.26; P = 0.618).
CONCLUSIONS: Prehospital prediction of mortality after TBI was good with both models, and the NACA-BM was not inferior to the GCS-RM. Prediction of IC-14 was moderate in both models.