Quality of randomised controlled trials in head injury

doi:10.1136/bmj.321.7262.704

BMJ 2000;321:704 ( 16 September )

Letters

Quality of randomised controlled trials in head injury

Statistical power can be increased

More trials are needed

Statistical power can be increased

The first 150 words of the full text of this article appear below.

EDITOR $---$ We agree with Dickinson et al¹ that larger and better designed randomised controlled trials are necessary to detectbenefits of treatment in head injury.² But increasing the samplesize is not the only solution to show efficacy. The statisticalpower of a study can also be improved by randomising the samenumber of patients but taking prognostic factors, such as ageor Glasgow coma scale, intoaccount.

Firstly, one might limit the inclusion of patients to those with an intermediate prognosis $---$ for example, between 20% and 80%probability of a favourable outcome.³ This leads to a focuson patients for whom treatment effects can be well determined.For the same power, a reduction in sample size of 30% might beachievable.³ After showing efficacy in the intermediate riskgroup, additional funding may be raised more easily to study patientswith a poorer or better prognosis. Note that this . . . [Full text of this article]

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Size and quality of randomised controlled trials in head injury: review of published studies: Karen Dickinson, Frances Bunn, Reinhard Wentz, Phil Edwards, and Ian Roberts
BMJ 2000 320: 1308-1311. [Abstract] [Full Text] [PDF]

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Boto, G R, Gomez, P A, De La Cruz, J, Lobato, R D (2006). Severe head injury and the risk of early death. J. Neurol. Neurosurg. Psychiatry 77: 1054-1059 [Abstract] [Full text]