Table 3.

Prediction Model Performance for 6-Month Mortality

Prediction model	Discrimination AUC (95% CI) H-L p value	Calibration	Precision Brier score
All patients (n=890)
APACHE IIa	0.80 (0.77–0.84)	0.099	0.139
IMPACT corea	0.80 (0.77–0.83)	<0.001	0.140
IMPACT extendeda	0.80 (0.77–0.83)	<0.001	0.144
IMPACT laba	0.81 (0.78–0.84)	0.054	0.136
Development sample (n=450)
APACHE IIa	0.80 (0.75–0.84)	0.364	0.137
IMAPCT corea	0.78 (0.73–0.84)	0.030	0.137
IMPACT extendeda	0.79 (0.74–0.84)	0.001	0.143
IMPACT laba	0.80 (0.76–0.85)	0.103	0.133
IMPACTcore-APACHE II	0.84 (0.79–0.88)	0.915	0.117
IMPACText-APACHE II	0.84 (0.79–0.88)	0.366	0.119
IMPACTlab-APACHE II	0.84 (0.80–0.88)	0.727	0.119
Validation sample (n=450)
APACHE IIa	0.81 (0.76–0.86)	0.315	0.142
IMAPCT corea	0.81 (0.77–0.86)	0.063	0.143
IMPACT extendeda	0.81 (0.76–0.86)	0.026	0.144
IMPACT laba	0.82 (0.77–0.86)	0.441	0.138
IMPACTcore-APACHE II	0.84 (0.80–0.89)	0.690	0.125
IMPACText-APACHE II	0.84 (0.80–0.89)	0.515	0.123
IMPACTlab-APACHE II	0.85 (0.81–0.89)	0.198	0.123

The predicted risk of 6-month mortality using the new models can be calculated by the equation: 1/(1+e^-logit), where the logit is defined as:

logit_{IMPACTcore-APACHE II}=−6.004+0.234 ^* IMPACTcore sumscore+0.160 ^* APACHE II score

logit_{IMPACText-APACHE II}=−6.265+0.193 ^* IMPACText sumscore+0.158 ^* APACHE II score

logit_{IMPACTlab-APACHE II}=−6.516+0.187 ^* IMPACTlab sumscore+0.149 ^* APACHE II score

^aOriginal models.

AUC, area under the curve; CI, confidence interval; H-L, Hosmer-Lemeshow Ĉ-test (goodness of fit); APACHE, Acute Physiology and Chronic Health Evaluation; IMPACT, International Mission for Prognosis and Analysis of Clinical Trials in TBI.