• Michael Callaham, Robert L Wears, and Ellen Weber.
• Division of Emergency Medicine, University of California, San Francisco, CA 94143-0208, USA. mlc@medicine.ucsf.edu
• JAMA. 2002 Jun 5; 287 (21): 284728502847-50.

ContextCitation by other authors is important in the dissemination of published science, but factors predicting it are little studied.MethodsTo identify characteristics of published research predicting citation in other journals, we searched the Science Citations Index database for a standardized 3.5 years for all citations of published articles originally submitted to a 1991 emergency medicine specialty meeting. Analysis was conducted by classification and regression trees, a nonparametric modeling technique of regression trees, to determine the impact of previously determined characteristics of the full articles on the outcome measures. We calculated the the number of times an article was cited each year and calculated the mean impact factor (citations per manuscript per year) in other citing journals.ResultsOf the 493 submitted manuscripts, 204 published articles met entry criteria. The mean citations per year was 2.04 (95% confidence interval, 1.6-2.4; range, 0-20.9) in 440 different journals. Nineteen articles (9.3%) were never cited. The ability to predict the citations per year was weak (pseudo R(2) = 0.14.). The strongest predictor of citations per year was the impact factor of the original publishing journal. The presence of a control group, the subjective newsworthiness score, and sample size predicted citation frequency (24.3%, 26.0%, and 26.5% as strongly, respectively). The ability to predict mean impact factor of the citing journals was even weaker (pseudo R(2) = 0.09). The impact factor of the publishing journal was the strongest predictor, followed by the newsworthiness score (89.9% as strongly) and a subjective quality score (61.5%). Positive outcome bias was not evident for either outcome measure.ConclusionIn this cohort of published research, commonly used measures of study methodology and design did not predict the frequency of citations or the importance of citing journals. Positive outcome bias was not evident. The impact factor of the original publishing journal was more important than any other variable, suggesting that the journal in which a study is published may be as important as traditional measures of study quality in ensuring dissemination.

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