traumatic brain injury ( tbi ) is a field in medicine with one of the greatest unmet needs . severe injuries constitute a leading cause of death and disability worldwide , with devastating effects on patients and their relatives and high socioeconomic costs . tbi is a heterogeneous disease in terms of cause , pathology , severity and prognosis . this was recently illustrated in the impact project ( international mission on prognosis and clinical trial design in tbi ) in which individual patient data from three observational series and eight clinical trials were merged into a large registry , forming a culture medium for exploring concepts to improve the design of clinical trials in tbi . creating this registry involved over 10 person years of work due to the widely differing structure of the study datasets , poor documentation and variability in coding . lack of standardization has been a major factor confounding comparisons between studies , and complicating meta - analyses of individual patient data . analysing individual patient data across studies may well be key to advancing the clinical field of tbi , and improving treatment . this uncertainty is reflected in the paucity of class i and ii evidence underpinning authoritative guideline recommendations . although randomized controlled trials remain the prime approach for investigating treatment effects , these are costly and logistically demanding . consequently , it seems unlikely that we can mount adequately powered trials to study all relevant treatment modalities . pooling data from multiple studies can provide an alternative source of evidence that can be realistically obtained in a cost - efficient way . relating differences in trauma organization and treatment approaches to outcome will permit both better targeting of prevention and exploration of reasons for observed differences . further , this approach provides a means of generating and refining hypotheses , and ranking them in importance for testing . the great potential of performing a meta - analysis of individual patient data was demonstrated by the impact studies . simulation studies showed that the statistical power in tbi trials may be increased up to 50% by utilizing more efficient approaches to the analysis . extensive prognostic analysis defined the strength of many known predictors more precisely , yielded new predictors and has resulted in validated prognostic models for use in moderate and severe tbi . the benefit of analyzing large numbers of patients was also demonstrated in the development of prognostic models based on the crash trial . these models are useful for providing information on expectations of outcome , for classifying the severity of brain injury , for stratification and covariate adjustment in clinical trials , and as reference for evaluating quality of care . standardization of data collection and coding is essential to facilitate sharing of results and to analyze data across studies . initial steps undertaken by the impact study group towards development of standardization were integrated in the us into a much larger interagency initiative towards ' an integrated approach to research in psychological health and traumatic brain injury ' . this initiative included working groups on demographics and clinical assessment , biomarkers , neuroimaging and outcome . the global aim was to develop recommendations on selection and coding of data elements for studies across the broad spectrum of tbi . the process was consensus driven , with multidisciplinary input from a broad range of experts , covering the entire trauma chain from emergency medicine to rehabilitation and late outpatient care . recommendations were formulated and templates produced summarizing coding formats , motivation of choices and procedures . for example , the data elements ' age , gender and race ' are contained in the module ' demographics ' under the category ' subject characteristics ' . as the required level of detail may vary greatly with the aim of a specific study , three versions for coding data elements were developed : a basic , an advanced , and an extended format with the greatest level of detail in the extended version . the coding of these versions is such that more detailed coding can be collapsed into the basic version , thus facilitating comparison across studies . the draft recommendations and templates are available from the author and will be posted on the web in early 2010 . this work presents a major advance towards standardisation , but has not yet addressed approaches to analysis of parameters such as intracranial pressure that are continuously monitored in the icu setting . here , we strongly advocate further development of software aimed at capturing the frequency distribution of measured values during continuous monitoring and further research into the best approaches to analysis . these developments may well constitute one of the most important steps forward in the field of clinical trials in tbi , paving the road for harvesting successful results in the near future . grant support was provided by nih - ninds ( ns 042691 ) and further funded as part of the interagency initiative in the us towards ' an integrated approach to research in psychological health and traumatic brain injury ' . this commentary is based upon extensive collaborative work , performed by the impact study group and the interagency working group on demographics and clinical assessment . grant support was provided by nih - ninds ( ns 042691 ) and further funded as part of the interagency initiative in the us towards ' an integrated approach to research in psychological health and traumatic brain injury ' .
great variability exists in data collection and coding of variables in studies on traumatic brain injury ( tbi ) . 
 this confounds comparison of results and analysis of data across studies . 
 the difficulties in performing a meta - analysis of individual patient data were recently illustrated in the impact project ( international mission on prognosis and clinical trial design in tbi ) : merging data from 11 studies involved over 10 person years of work . 
 however , these studies did confirm the great potential for advancing the field by this approach . 
 although randomized controlled trials remain the prime approach for investigating treatment effects , these can never address the many uncertainties concerning multiple treatment modalities in tbi . 
 pooling data from different studies may provide the best possible source of evidence we can get in a cost efficient way . 
 standardisation of data collection and coding is essential to this purpose . 
 recommendations hereto have been proposed by an interagency initiative in the us . 
 these proposals deserve to be taken forward at an international level . 
 this initiative may well constitute one of the most important steps forwards , paving the road for harvesting successful results in the near future .