Evaluating the Performance of the IMPACT Model in the Prehospital TXA for TBI Trial (P14-7.001)

Abstract

<h3>Objective:</h3> To test the IMPACT model’s performance in a contemporary clinical trial population. <h3>Background:</h3> The International Mission on Prognosis and Analysis of Clinical Trials in Traumatic Brain Injury (IMPACT) prognostic model predicts functional outcome after moderate-severe traumatic brain injury (TBI). Our previous work suggested that glial fibrillary acidic protein (GFAP) may improve the discrimination of outcome when added to prognostic models. <h3>Design/Methods:</h3> We analyzed data from a subset subjects from the phase II double-blind, multicenter randomized controlled trial, “Prehospital Tranexamic Acid Use for Traumatic Brain Injury.” This subset was limited to subjects in the placebo arm of the parent trial with evidence of hemorrhage on initial head computed tomographic (CT) scan. All 3 versions (core, extended, lab) of the IMPACT model were evaluated against 6-month mortality, plus an exploratory 4^th version (lab+GFAP). We compared our results to previously published validation results from the CENTER-TBI cohort. <h3>Results:</h3> Within the subset (n=166), 127 subjects had complete 6-month outcome data. Predictor variables were missing &lt;10% (0–9.4%) of cases, and were imputed (GCS motor score, pupillary reactivity, serum glucose, serum hemoglobin, hypoxia, and Marshall CT score). GFAP was associated with mortality (p=0.004). The core model discriminated poorly in the subset (AUC 0.60 [95% CI: 0.48–0.71], p=0.096). The extended model discriminated well (AUC 0.73 [95% CI: 0.64–0.82], p&lt;0.001). The lab model discriminated non-significantly better (AUC 0.76 [95% CI: 0.66–0.86], p=0.167). Adding GFAP to the lab model improved discrimination further (AUC 0.83 [95% CI: 0.76–0.90], p=0.004). All 4 models overestimated mortality compared with the observed rate (n=31, 24% v. 26–82%). <h3>Conclusions:</h3> In comparison with the observational CENTER-TBI validation cohort, the IMPACT models (core/extended/lab) discriminated mortality less well in a subset of the TXA trial. The addition of GFAP improved discrimination for mortality, but further work is needed to optimize its addition to the lab model. <b>Disclosure:</b> Dr. Hinson has received personal compensation in the range of $500-$4,999 for serving on a Scientific Advisory or Data Safety Monitoring board for Biogen. Dr. Hinson has received personal compensation in the range of $10,000-$49,999 for serving as an Editor, Associate Editor, or Editorial Advisory Board Member for UCSF. Dr. Hinson has received personal compensation in the range of $10,000-$49,999 for serving as an Editor, Associate Editor, or Editorial Advisory Board Member for American Heart Association. Shannon McWeeney has nothing to disclose. Adam Ferguson has received personal compensation in the range of $500-$4,999 for serving on a Scientific Advisory or Data Safety Monitoring board for Spine X Inc. Adam Ferguson has received personal compensation in the range of $5,000-$9,999 for serving on a Scientific Advisory or Data Safety Monitoring board for Neuronasal Inc.. The institution of Adam Ferguson has received research support from NIH/NINDS. The institution of Adam Ferguson has received research support from VA RR&amp;D. The institution of Adam Ferguson has received research support from VA BLR&amp;D. The institution of Adam Ferguson has received research support from Wings for Life Foundation/Craig H Neilsen Foundation. The institution of Adam Ferguson has received research support from Wings for Life Foundation. The institution of Adam Ferguson has received research support from DoD/CDMRP. The institution of Adam Ferguson has received research support from DARPA. The institution of Adam Ferguson has received research support from DoE. Adam Ferguson has received personal compensation in the range of $500-$4,999 for serving as a Reviewer with NIH/CSR. Dr. Schreiber has received personal compensation in the range of $5,000-$9,999 for serving as a Consultant for CSL Behring. Dr. Schreiber has received personal compensation in the range of $10,000-$49,999 for serving as a Consultant for Harmonetics. Dr. Schreiber has received personal compensation in the range of $500-$4,999 for serving as a Consultant for Tricol. Dr. Schreiber has received personal compensation in the range of $0-$499 for serving as an Editor, Associate Editor, or Editorial Advisory Board Member for Trauma Textbook. Dr. Schreiber has received personal compensation in the range of $10,000-$49,999 for serving as an Expert Witness for Lawyers. The institution of Dr. Schreiber has received research support from DoD. Dr. Rowell has nothing to disclose.