THE EFFECT OF BLINDING AND UNMASKING ON THE QUALITY
OF PEER REVIEW: A RANDOMIZED CONTROLLED TRIAL
Susan van Rooyen, Fiona Godlee, Stephen Evans, Richard Smith, and Nick Black
BMJ, BMA House, Tavistock Sq, London WC1H 9JR, UK; London School of Hygiene & Tropical Medicine, London, UK
Objective: To see whether concealing authors' identities from reviewers (blinding) and/or revealing the
reviewer's identity to a coreviewer (unmasking) affects the quality of reviews.
Design: Randomized controlled trial. Papers were sent to 2 reviewers and randomized as to whether the
reviewers were asked to allow their signed reviews to be sent to their co-reviewer. Reviewers were then randomized
to receive either a blinded or an unblinded paper. Two editors independently evaluated the reviews using a validated instrument.
Results: To date 487 papers have been entered into the study. Of these, 26 (5.3%) were excluded after randomization.
Preliminary analysis showed that the mean overall quality score was 20.0 (possible range 7 to 35; 95% CI, 19.5-20.5).
There was no significant difference in overall quality, recommendation regarding publication, or time taken to review between
different groups. Data collection is continuing.
Conclusions: Blinding and masking made no difference in quality, reviewers' recommendation, or time taken to review.
Decisions on whether to change established practice must be based on other considerations, and other interventions to improve
the quality of peer review need to be explored.
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