Size and quality of randomised controlled trials in head injury: review of published studies
Many millions of people are treated world-wide each year for severe head injury and there are few treatments of established effectiveness. A study in this week's BMJ reports that currently available trials of treatment are too small and too poorly designed to detect or refute reliably moderate but important benefits or hazards of treatment.
Researchers from the Cochrane Injuries Group looked at 208 separate randomised controlled trials with an average number of 82 patients per trial. Doctors treating severe head injuries recognise that improvements in health outcomes of only a few per cent would be important because of the large numbers of patients involved, but most clinical trials would miss treatment effects of this size.
The BMJ paper states: "If a widely practicable treatment reduced the risk of death or disability by 5% then treatment of one million patients would protect 50,000 people from death or disability." None of the trials studied was large enough to detect reliably a 5% absolute reduction in the risk of disability or death. The study's authors say large scale randomised controlled trials could be of considerable importance to public health but that the limited funding for head injury research has been a major obstacle to conducting these trials.
Contact:
Frances Bunn, Cochrane Injuries Group, Institute of Child Health Email: F.bunn@ich.ucl.ac.uk