How to appraise clinical trials

Treatment decisions should be based on data from randomized controlled trials. However, trials are susceptible to bias, and there may be important limitations to the data. Critical appraisal of such studies will need to consider both the methodological rigour of the study and the applicability of the results to real-life clinical practice. Instead of simply glancing at the abstract, readers should work systematically through the trial report. The first port of call should be to establish the aims of the study, and then to consider whether the methods used are able to provide an unbiased answer. Particular attention should be directed towards patient allocation ensuring that the study groups are well balanced. Readers should check that the follow-up is adequate, and that there is sufficient blinding of investigator and participants so that preconceived notions do not influence recording of outcomes. The Results section should be reviewed in the light of the trial's objectives to confirm that the researchers have reported all data (positive or negative) that are relevant to the study question. Trials are scientific experiments with specific aspects that can markedly differ from real-life clinical practice. The results in a trial may not be achievable in a different treatment environment, or with less highly selected patients. Sophisticated treatment regimens in the trial may be difficult to deliver in daily practice. All of these potential differences should be considered when evaluating clinical trial results.