Skip to main content

Predictive ability of the IMPACT-TBI prognostic model is improved by adding markers of coagulation


One of the most used prognostic models for traumatic brain injury is the IMPACT-TBI model, which predicts 6-month mortality and unfavorable outcome. Our aim was to study whether adding markers of coagulation improves the model's predictive power when accounting for extracranial injury.


Patients with a TBI admitted to a designated trauma center in 2009/10 were screened retrospectively and included according to the IMPACT study criteria. The predictive outcome was calculated for included patients using the full IMPACT-TBI model. To assess coagulopathy and extracranial injury we used the prothrombin time percentage (PT), platelet count (109), and injury severity score (ISS). PT, platelets and ISS were added to the IMPACT model, creating new models. The predictive power of the new models was tested by comparing their area under the receiver operating characteristic curve (AUC) with the original model.


Totally 342 were included. Six-month mortality was 32% and unfavorable outcome 57%. The IMPACT model's predictive power for mortality and neurological outcome; AUC: 0.85, CI: 0.81 to 0.89; and AUC: 0.81, CI: 0.76 to 0.86. Nonsurvivors and patients with an unfavorable outcome had lower platelets (159; 165 vs. 191; 198), PT (76; 77 vs. 86; 90) and higher ISS (50; 44% ISS >25 vs. 34; 32% ISS >25) compared with survivors and favorable outcome (P < 0.05). Addition of PT but not ISS nor platelets resulted in a significant improvement of the IMPACT model's predictive power for 6-month mortality; AUC: 0.87, CI: 0.81 to 0.89, P = 0.017 (Figure 1). In multivariate analysis PT remained an independent significant predictor of outcome when adjusting for IMPACT prognosis and ISS (OR: 0.985, CI: 0.975 to 0.996).


Addition of PT to the IMPACT model improves the predictive power for 6-month mortality but not neurological outcome when adjusting for ISS.

Figure 1

(abstract P322)


  1. 1.

    Steyerberg EW, et al.: PLoS Med. 2008, 5: e165. 10.1371/journal.pmed.0050165

    PubMed Central  Article  PubMed  Google Scholar 

  2. 2.

    Marmarou A, et al.: J Neurotrauma. 2007, 24: 239-250. 10.1089/neu.2006.0036

    Article  PubMed  Google Scholar 

Download references

Author information



Corresponding author

Correspondence to R Raj.

Rights and permissions

This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or other third party material in this article are included in the article's Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit The Creative Commons Public Domain Dedication waiver ( applies to the data made available in this article, unless otherwise stated in a credit line to the data.

Reprints and Permissions

About this article

Cite this article

Raj, R., Siironen, J., Kivisaari, R. et al. Predictive ability of the IMPACT-TBI prognostic model is improved by adding markers of coagulation. Crit Care 17, P322 (2013).

Download citation


  • Traumatic Brain Injury
  • Predictive Power
  • Prothrombin Time
  • Neurological Outcome
  • Injury Severity Score