Blinded peer review of research, in which the author's identity and institutional affiliation are concealed from the reviewer, is commonly used to reduce the influence of other criteria such as geographic location or institutional prestige, but little is known about its effectiveness at reducing bias. The authors of this paper evaluated the effect of blinded review on the association between abstract characteristics and likelihood of abstract acceptance by comparing abstracts submitted for a national research meeting under an open review system in place from 2000-2001 and a blinded review system used from 2002-2004. Abstracts were categorized by country, primary language, institution prestige, author sex, and government and industry status. Evidence emerged of bias in the open review of abstracts, favoring authors from the United States, English-speaking countries outside the United States and prestigious academic institutions. Bias favoring authors from U.S. government agencies and authors not from private industry appeared likely as well. While blinded review at least partially reduced reviewer bias, it did not eliminate differences in the likelihood of abstract acceptance.
The authors speculate that associations found in the blinded review results may reflect true differences in the quality of research or institutional characteristics and funding opportunities. Adoption of blinded peer review by scientific research meetings is a reasonable, low-cost intervention with substantial benefit. Future research should evaluate the effect of blinded peer review on manuscript review, which may be less susceptible to reviewer bias.