Design and statistical issues in multicenter trials of severe head injury.

Multicenter clinical trials are the most powerful agent to evaluate new therapies in medicine, but have failed to impact traumatic brain injury, in which at least 20 such trials have been performed, without a positive result. Such trials need to be carefully planned, with a run-in period to ensure center compliance. Stratification, careful monitoring, adequate sample size, interim analysis and adequate numbers of patients per center are all vital requirements for a useful outcome in such trials.