Predicting Outcomes after Severe and Moderate Traumatic Brain Injury: An External Validation of Impact and Crash Prognostic Models in a Large Spanish Cohort

Prognostic models that were developed by the International Mission on Prognosis and Analysis of Clinical Trials in Traumatic Brain Injury (IMPACT) study group and the Corticosteroid Randomization After Signification Head injury (CRASH) collaborators are the most commonly used prognostic models for outcome after traumatic brain injury (TBI). Although they have been considered to be useful tools in clinical practice, a continuous process of external validation in recent cohorts of different populations is necessary. The objective of this study was to determine the external validity and compare the IMPACT and CRASH-refitted models for prediction of outcomes after moderate or severe TBI in a nonselected 1301-patient Spanish cohort. We studied discrimination, calibration, and overall fit as external validation measures. Excellent discrimination was indicated (area under the curve [AUC] 0.78-0.87) by the higher values in the validation than in the development sample for both models and outcomes. Calibration revealed that IMPACT models, in general, predict lower probabilities of both outcomes (mortality and disability). In contrast, CRASH-refitted models provided higher predicted probabilities than those observed. We can conclude that both models demonstrate an adequate performance in our representative traumatic brain Mediterranean population. Therefore, these models can be sensibly applied in our clinical practice so long as their limitations are observed during individual outcome prediction.