The current movement towards evidence-based medical practice involves integrating individual clinical expertise with the explicit and informed use of the best available external clinical evidence from a systematic review of published research, to reach decisions about the care of individual patients.1 The recent creation of a Centre for Evidence-Based Child Health in London, UK illustrates the increasing priority given to these activities within paediatric practice.2 The clinical evidence from published research comprises patient centred clinical research in a number of areas, including the accuracy and precision of diagnostic tests, the power of prognostic markers, and the efficacy and safety of therapeutic, rehabilitative, and preventive regimens. Randomised controlled trials (RCTs) are the gold standard for scientific studies in the last category, including those evaluating the effect of treatment. The primary advantage of RCTs is that when treatments are allocated at random in a sample of sufficiently large size, the results are likely to achieve a level of validity that is not possible to attain with other study designs. RCTs are therefore being used increasingly to evaluate the effectiveness of health care interventions.3

Recognising that RCTs provide the best evidence in comparisons of treatment, rehabilitative or preventive regimens, the Cochrane Collaboration has established an international network of centres that systematically attempt to identify, document, and make available for reference all published and unpublished RCTs.4 The impact of this global initiative in improving the outcome of clinical practice will be dependent on the extent to which clinicians change their practice in the light of available medical evidence. The formation in the UK of the Cochrane Collaborative Review Group on Effective Professional Practice, which focuses on reviews of effectiveness of different approaches to implementation of evidence-based clinical guidelines,5 and the NHS centre for the dissemination of reviews are two …