Clinical Trials

■■❚❙❘Chapter 6Source and Controlof BiasRadivoj Arezina and Duolao WangThe aim of a randomized controlled trial is to provide unbiasedevaluation of the efficacy and safety of a medicinal product ora therapeutic procedure. Unfortunately, the treatment effectestimates generated in a study are rarely free of all bias. Thisis due to a number of biases or errors that occur during a studyfrom conception, through conduct, to completion of the trial,and even beyond the end of the trial when communicating trialresults. These contributing factors can be classified into threecategories: bias, confounding, and random error. In this chapter,we provide an overview of the ways in which bias can enter atdifferent stages of a clinical trial and review ways of minimizingbias in clinical research.55