How to appraise clinical trials

Treatment decisions should be based on reliable data. However, randomized controlled trials are susceptible to bias and other important limitations. Critical appraisal of such studies must consider both the methodological rigour of the study and the applicability of the results to routine clinical practice. Readers should work systematically through trial reports. They should establish the aims of the study and 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. There should be adequate follow-up and sufficient blinding of the 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. Critical appraisers should also consider how closely the conditions of the trial (e.g. selection of patients, follow-up arrangements) reflect real-world medicine, allowing the results to be generalizable to routine clinical practice.