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January 15, 2019

Challenges of Non–Intention-to-Treat Analyses

Author Affiliations
  • 1Department of Biostatistics and Medical Informatics, University of Wisconsin–Madison, Madison
JAMA. 2019;321(2):145-146. doi:10.1001/jama.2018.19192

Over the past 5 decades, the randomized clinical trial has become the gold standard for evaluation of the risks and benefits of new interventions, including drugs, medical devices, and surgical procedures.1

To justify the use of randomization, it is important to note that in a nonrandomized study comparing 2 interventions, a small P value (of which P < .05 is generally considered statistically significant) for a statistical comparison between groups can be due to 1 of 3 sources: chance, causation, or confounding. Because randomized assignments cannot be associated with participant characteristics, effective randomization eliminates the third possibility, enabling direct assessment of potential causal relationships provided that the study is designed, conducted, and analyzed properly.

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