Clinical results and outcome improvement over time in traumatic brain injury

Prognostic models for traumatic brain injury (TBI) are important tools both in clinical practice and research if properly validated, preferably by external validation. Prognostic models also offer the possibility of monitoring performance by comparing predicted outcomes with observed outcomes. In this study, we applied the prognostic models developed by the International Mission on Prognosis and Analysis of Clinical Trials in TBI (IMPACT) in an Italian multi-center database (Neurolink) with two aims: to compare observed with predicted outcomes and to check for a possible improvement of clinical outcome over the 11 years of patient inclusion in Neurolink. We applied the IMPACT models to patients included in Neurolink between 1997 and 2007. Performance of the models was assessed by determining calibration (with calibration plots) and discrimination (by the area under the receiver operating characteristic curve [AUC]). Logistic regression analysis was used to analyze a possible trend in outcomes over time, adjusted for predicted outcomes. A total of 1401 patients were studied. Patients had a median age of 40 years and 51% had a Glasgow Coma Scale motor score of 5 or 6. The models showed good discrimination, with AUCs of 0.86 (according to the Core Model) and 0.88 (Extended Model), and adequate calibration, with the overall observed risk of unfavorable outcome and mortality being less than predicted. Outcomes significantly improved over time. This study shows that the IMPACT models performed reasonably well in the Neurolink data and can be used for monitoring performance. After adjustment for predicted outcomes with the prognostic models, we observed a substantial improvement of patient outcomes over time in the three Neurolink centers.