External Validation of the CRASH and IMPACT Prognostic Models in Severe Traumatic Brain Injury

Abstract

An accurate prognostic model is extremely important in severe traumatic brain injury (TBI) for both patient management and research. Clinical prediction models must be validated both internally and externally before they are considered widely applicable. Our aim is to independently externally validate two prediction models, one developed by the Corticosteroid Randomization After Significant Head injury (CRASH) trial investigators, and the other from the International Mission for Prognosis and Analysis of Clinical Trials in Traumatic Brain Injury (IMPACT) group. We used a cohort of 300 patients with severe TBI (Glasgow Coma Score [GCS] ≤8) consecutively admitted to the National Neuroscience Institute (NNI), Singapore, between February 2006 and December 2009. The CRASH models (base and CT) predict 14 day mortality and 6 month unfavorable outcome. The IMPACT models (core, extended, and laboratory) estimate 6 month mortality and unfavorable outcome. Validation was based on measures of discrimination and calibration. Discrimination was assessed using the area under the receiving operating characteristic curve (AUC), and calibration was assessed using the Hosmer-Lemeshow (H-L) goodness-of-fit test and Cox calibration regression analysis. In the NNI database, the overall observed 14 day mortality was 47.7%, and the observed 6 month unfavorable outcome was 71.0%. The CRASH base model and all three IMPACT models gave an underestimate of the observed values in our cohort when used to predict outcome. Using the CRASH CT model, the predicted 14 day mortality of 46.6% approximated the observed outcome, whereas the predicted 6 month unfavorable outcome was an overestimate at 74.8%. Overall, both the CRASH and IMPACT models showed good discrimination, with AUCs ranging from 0.80 to 0.89, and good overall calibration. We conclude that both the CRASH and IMPACT models satisfactorily predicted outcome in our patients with severe TBI.

Outcome Prediction after Traumatic Brain Injury: Comparison of the Performance of Routinely Used Severity Scores and Multivariable Prognostic Models

“…[8] It has been established as a prognostic model of choice by a number of external validation studies[124142] (including a study on a population which was used for this study),[11] which justifies its use as a gold standard in this paper.…”

Systematic Review of Traumatic Brain Injury and the Impact of Antioxidant Therapy on Clinical Outcomes

“…Population variability and the diversity of injury in various clinical studies have prevented clear conclusions about the use of antioxidant therapies with TBI patients (Rapp, Cellucci, Keyser, Gilpin, & Darmon, 2013). The two major studies related to TBI prognosis (the Corticosteroid Randomization After Significant Head Injury and the International Mission for Prognosis and Analysis of Clinical Trials in Traumatic Brain Injury) have not addressed the underlying TBI causality or pathophysiology (Han, King, Neilson, Gandhi, & Ng, 2014;Roozenbeek et al, 2012). Promising TBI research has identified neuron inflammation and oxidative stress as major factors involved with secondary injury, raising the possibility that antioxidants could alter the clinical progression (Bains & Hall, 2012).…”

Prognostic models in traumatic brain injury

“…18 Th ird, several previous studies have shown similar predictive ability of IMPACT and CRASH. 9,10,164,165 Th us, it is highly presumable that CRASH and IMPACT would have equaled in predictive value in the present datasets as well. Fourth, CRASH was not designed to predict 6-month mortality, which may limit its use in observational studies where the possibility of assessing neurological outcome is oft en limited.…”