Date Published: August 5, 2008
Publisher: Public Library of Science
Author(s): Neil H Young, Peter J. D Andrews
Abstract: Peter Andrews and Neil Young discuss the implications of a study involving the development and validation of new prognostic models for traumatic brain injury.
Partial Text: Traumatic brain injury (TBI) is a major cause of death and disability throughout the world. The annual incidence of TBI in the United States has been estimated at between 180 and 250 per 100,000 population per year . TBI is the cause of one third to one half of all trauma deaths, and the leading cause of disability in people under 40, severely disabling 15 to 20 per 100,000 population per year . Injuries, including TBI, are projected to account for 20% of the worldwide burden of death and disability by 2020 .
Prognostic models are statistical models that combine data from patients to predict clinical outcome. Such models based on data collected soon after presentation could in theory be used to aid early clinical decision making and to allow more accurate counselling of patients’ families. They could also have a pivotal role in the future design and analysis of randomised controlled trials, and assist in clinical audit by allowing adjustment for case mix .
In recent years, there have been two milestones that helped forward research into TBI: the formation of the IMPACT (International Mission on Prognosis and Analysis of Clinical Trials in TBI) database , and the CRASH (Corticosteroid Randomisation After Significant Head Injury) trial . The IMPACT database combined patient data from eight randomised controlled clinical trials and three observational studies to give a patient population of over 9,000. The CRASH trial was a randomised controlled trial of the effect of early steroid administration on outcome after TBI. The CRASH trial enrolled 10,008 patients and is the largest clinical trial ever conducted in patients with TBI.
While the predictors of age, motor score, and pupillary reactivity have been included in many prognostic models for TBI, Steyerberg and colleagues’ models  and the models produced by the CRASH collaborators  are the largest and most robustly validated that have been developed so far. They are also readily accessible to clinicians via a Web-based calculator [9,10].
We now have new prognostic models for TBI developed from large numbers of patients, which have been externally validated to allow prediction between favourable or unfavourable outcome at six months [7,8]. These models may provide useful additional information in regard to clinical decision making and the counselling of patients’ relatives, but it must be remembered that their outcomes apply to populations—and so great caution is needed if applying them to individual patients. These models will undoubtedly be of great use in clinical audit, allowing comparison between different units and changes in management over time, while allowing for different case mix. The models should also allow better trial design and analysis: many patients with TBI previously included in clinical trials have expected outcomes that are so good or bad that no intervention could be expected to alter the outcome . Future clinical trials could focus on those patients with a more uncertain prognosis.