Determining the impact factors of secondary journals: A retrospective cohort study

Secondary journals such as Evidence-Based Medicine, ACP Journal Club, and Evidence-Based Nursing summarize, from over 150 clinical journals, articles that pass criteria for scientific merit, clinical relevance, and interest to practicing clinicians. We performed a retrospective cohort study to validate the selection process used to produce the secondary journals by calculating the 2007 impact factors for these journals using articles that were abstracted and originally published in 2005–2006. The ‘impact factors’ for the secondary journals were calculated using 2007 citations to included articles. These were compared to the published impact factors and mean citations of the source journals. 2005/2006 articles in the secondary journals were originally published in 82 journals with ISI impact factors (median 4.1, range 0.85–52.9). The calculated impact factors for the secondary journals were 39.5 for ACP Journal Club, 30.2 for Evidence-Based Medicine, and 9.3 for Evidence-Based Nursing. Limitations include articles coming from only 150 journal titles and the inclusion of these articles may in fact stimulate citations. We conclude that evidence-based secondary journals include articles at the time of publication that go on to garner more citations on average than other articles in the source publications.