Table 4.

Prediction Model Performance for 6-Month Unfavorable Neurological Outcome

Prediction model	Discrimination AUC (95% CI)	Calibration H-L p value	Precision Brier score
All patients (n=842)
APACHE IIa	0.76 (0.73–0.79)	<0.001	0.248
IMPACT corea	0.78 (0.75–0.81)	<0.001	0.193
IMPACT extendeda	0.79 (0.76–0.82)	0.006	0.190
IMPACT laba	0.79 (0.76–0.82)	0.078	0.188
Development sample (n=421)
APACHE IIa	0.74 (0.69–0.79)	<0.001	0.250
IMAPCT corea	0.75 (0.71–0.79)	<0.001	0.234
IMPACT extendeda	0.76 (0.72–0.80)	0.008	0.202
IMPACT laba	0.76 (0.72–0.81)	0.008	0.199
IMPACTcore-APACHE II	0.78 (0.74–0.82)	0.283	0.190
IMPACText-APACHE II	0.79 (0.74–0.83)	0.327	0.188
IMPACTlab-APACHE II	0.79 (0.74–0.83)	0.318	0.188
Validation sample (n=421)
APACHE IIa	0.78 (0.74–0.82)	<0.001	0.245
IMAPCT corea	0.81 (0.77–0.85)	<0.001	0.227
IMPACT extendeda	0.82 (0.78–0.85)	0.221	0.177
IMPACT laba	0.82 (0.78–0.86)	0.712	0.177
IMPACTcore-APACHE II	0.83 (0.79–0.87)	0.476	0.170
IMPACText-APACHE II	0.83 (0.80–0.87)	0.037	0.167
IMPACTlab-APACHE II	0.83 (0.80–0.87)	0.439	0.168

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

logit_{IMPACTcore-APACHE II}=−3.363+0.198 ^* IMPACTcore sumscore+0.113 ^* APACHE II score

logit_{IMPACText-APACHE II}=−3.551+0.175 ^* IMPACText sumscore+0.105 ^* APACHE II score

logit_{IMPACTlab-APACHE II}=−3.732+0.162 ^* IMPACTlab sumscore+0.099 ^* APACHE II score

^aOriginal models.

AUC, area under the curve; CI, confidence intervals; 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.