January 28, 1998

The Randomized Controlled Trial Gets a Middle-aged Checkup

Author Affiliations

From the Health Information Research Unit, Canadian Cochrane Network and Centre, McMaster Evidence-Based Practice Center, and Department of Clinical Epidemiology and Biostatistics, McMaster University, Toronto, Ontario (Dr Jadad). Dr Rennie is Deputy Editor (West), JAMA.

JAMA. 1998;279(4):319-320. doi:10.1001/jama.279.4.319

Although the first controlled trial in health care is thought to have occurred at least 3 centuries ago, the modern era of randomized controlled trials (RCTs) began in the late 1940s with the pioneering work of Bradford Hill.1 During this 50-year period, RCTs have made important contributions in health care and have been used extensively. Hundreds of thousands of RCTs have been published, and the doubling time in some research areas is less than 10 years.2 The main appeal of the RCT as a research tool in health care derives from its potential for reducing selection bias, particularly during the evaluation of diagnostic or therapeutic interventions. Researchers expect that randomization, if done properly, can keep study groups as similar as possible at the outset, thus enabling the investigators to isolate and quantify the effect of the interventions they are studying and control for other factors. No other study design allows researchers to balance unknown prognostic factors at baseline. Random allocation, however, does not protect RCTs against other types of bias.

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