Citation analysis of identical consensus statements revealed journal-related bias

Objective: To examine whether the prestige of a journal, measured by its impact factor, influences the numbers of citations obtained by published articles, independently of their scientific merit. Study Design and Setting: In this cohort study, citation counts were retrieved for articles describing consensus statements that were published in multiple journals and were correlated with the impact factors of the source journals. Results: Four consensus statements were published in multiple copies: QUOROM (QUality Of Reporting Of Meta-analyses) was published in three journals, CONSORT (CONsolidated Standards Of Reporting Trials) in eight journals, STARD (STAndards for Reporting of Diagnostic accuracy) in 14 journals, and STROBE (STrengthening the Reporting of OBservational studies in Epidemiology) in eight journals. For each consensus statement, the impact factor of the source journal and the number of citations were highly correlated (Spearman correlation coefficients: QUOROM, 1.00; CONSORT, 0.88; STARD, 0.65; and STROBE, 0.81-all P < 0.02). When adjusted for time since publication, each logarithm unit of impact factor predicted an increase of 1.0 logarithm unit of citations (95% confidence interval: 0.7-1.3, P < 0.001), and the variance explained was 66% (adjusted r(2) = 0.66). Conclusions: The prominence of the journal where an article is published, measured by its impact factor, influences the number of citations that the article will gather over time. Citation counts are not purely a reflection of scientific merit. (C) 2010 Elsevier Inc. All rights reserved.