Until recently, high-quality randomized controlled trials (RCTs) have rarely been performed in nephrology, because of several difficulties in conducting an RCT. The purpose of this article is to describe several issues related to the design and to the quality of RCTs in their conduct, analysis, interpretation, and reporting of the results. The advantage of an RCT is that, as a result of randomization, selection by prognosis by the clinician is prevented. However, not all RCTs provide a definitive answer on the research question that the investigators try to answer because of potential problems in their design, conduct and analysis. For example, the results of an RCT could be biased if the physicians and patients in the experimental and control groups were not sufficiently 'blinded'. Nevertheless, if conducted properly, RCTs remain the gold standard for studying the effects of therapy and other interventions.
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