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Related Experiment Videos

Ensuring the comparability of comparison groups: is randomization enough?

Vance W Berger1, Sherri Weinstein

  • 1National Cancer Institute, EPN, Suite 3131, 6130 Executive Boulevard, MSC-7354, Bethesda, MD 20892-7354, USA. vb78c@nih.gov

Controlled Clinical Trials
|October 7, 2004
PubMed
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Systematic selection bias can cause significant baseline imbalances in randomized trials, even when randomization is properly performed. Greater transparency in reporting is needed to assess and mitigate this bias in future research.

Area of Science:

  • Clinical Trials Methodology
  • Biostatistics
  • Research Integrity

Background:

  • Randomized trials are susceptible to selection bias, leading to systematic baseline imbalances.
  • This bias can occur despite proper randomization procedures.
  • Assessing and reporting on selection bias in trial reports is currently uncommon.

Purpose of the Study:

  • To highlight the prevalence of selection bias in randomized trials.
  • To emphasize the need for greater attention to this issue in scientific literature.

Main Methods:

  • Focused on trials previously identified as having potential selection bias or significant baseline imbalances.
  • Utilized existing reports and questioned trials for indicators of bias.

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Main Results:

  • Identified 14 randomized trials exhibiting suspicious signs of selection bias.
  • Acknowledged that this number may be an underrepresentation due to inconclusive data for other trials.

Conclusions:

  • Advocates for mandatory disclosure of allocation concealment and selection bias details in clinical trial reports.
  • Recommends considering a study's susceptibility to selection bias when evaluating its contribution to meta-analyses and decision-making.