Bibliometric analysis of case report citations and their effect on the impact factor: How does publishing case reports impact journals?

International audienceIntroductionGiven their low citation rate, case reports may reduce a journal's impact factor (IF), making a journal less likely to accept them for publication. However, this concept has never been proven in a bibliometric study. This led us to carry out a bibliometric analysis to evaluate (1) the exact number of case reports published in orthopedics over a 2-year period, (2) their citation rate, (3) what the journals’ IF would be if they had not published these case reports.HypothesisPublishing case reports reduces a journal's IF, bringing into question whether they should be published.Materials and methodsThis was a retrospective bibliometric study. We focused on all the articles influencing the year 2017. We looked at all the journals in the “Orthopedics” discipline that had published at least one article in the years n − 2 (= 2015) or n − 1 (= 2016).ResultsThere were 1925 case reports among the 28,903 articles published in all orthopedics journals in 2015–2016, a 6.7% share of publications. Individually, each case report in 2015–2016 was cited an average of 0.86 times ± 1.4 [0–13] in 2017. Of all the case reports published in 2015–2016, 571 (30%) had not been cited in 2017. When comparing the individual number of each case report citation to the journal's IF, we found 413 instances (21.5%) where the case report was cited more than expected and 1512 (78.5%) where it was cited less than expected based on the journal's IF. The mean IF was 2.013. If the journals had not published any case reports, the mean IF would have been 2.072 (p < 0.0001). For all the SIGAPS categories, the mean IF would have been higher if no case reports had been published. On average, the IF was lower by 0.059 points ± 0.121 [−0.165–0.537], with the difference being statistically significantly only for SIGAPS C and D journals. In 69 instances, the IF would be higher if the journal had not published any case reports. Conversely, the IF improved in 8 instances by publishing case reports: 3 were tier D journals and 5 were tier E journals.DiscussionOur study brings into question whether case reports should be published. Indeed, the publication of case reports lowers the IF of scientific journals. However, we should not completely stop publishing case reports since they can be useful to clinicians caring for patients with rare diseases or medical conditions.Level of evidenceIV, systematic retrospective study