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Br J Clin Pharmacol. 2016 April; 81(4): 786–788.
Published online 2016 January 14. doi:  10.1111/bcp.12832
PMCID: PMC4799912

Number of citations 1 year after publication of trial results and their relation to medicines regulatory approval

The number of citations of a paper depends on several factors such as, for instance, the topic addressed and the findings described. Mass media coverage could also play a role 1, although the media are more likely to cover observational studies rather than trials 2. Data have shown that the number of reprints seems to impact on the number of citations of articles 3. Industry order the vast majority of high reprint orders per article 4. Hence, it is not surprising that, 1 or more years after publication, industry‐sponsored trials are more cited than articles with other types of sponsorship 5, 6. The aim of this analysis was to assess if late medicine development industry‐funded trials are more cited than others 1 year after publication and to what extent the approval of the novel medicine/new indication by the US Food and Drug Administration (FDA) is related to the number of citations.

A cross‐sectional analysis of all registered trials published in The New England Journal of Medicine (NEJM), The Lancet and Journal of the American Medical Association (JAMA) in JanuaryJune 2014 issues was performed. The vast majority of medicine trials published in these journals were not open access papers at the time of publication. However, NEJM and JAMA provided free access online 6 months after publication on the journal website. Trial information pertaining to funding source, positive or negative results (as considered by the authors), clinical development phase, location and publication date were extracted from the article or registry. All articles reporting on late development (phases 2/3, 3 and 4) medicine trial results were included. The regulatory status of the medicine/indication being assessed in each trial was investigated. For new medicines/new indications approved by the FDA, the FDA press release dates were registered. The number of citations per article was extracted from Google Scholar and Web of Science.

A total of 72 articles were included in the analysis. Sixty‐four articles described trials conducted in high‐income countries (HICs) and eight in low and middle income countries (LMICs). Following Google Scholar data, among trials conducted in HICs, articles on industry‐funded medicine trials were more cited than non‐industry trials (median 28 vs. 17; P = 0.004). This was caused by differences in trials with positive results, whereas there were no differences in trials with negative results (Table 1). Non‐industry funded trials reporting negative results were more cited (median 37.5) than those with positive results (median 19), but the difference was not significant. Articles on FDA‐approved novel medicines/new indications were more cited (median 137.5) than other industry‐funded medicine trials yielding positive results (median 42) and non‐industry‐funded medicine trials reporting positive results (median 19).

Table 1
Number of citations* (median (upper, lower quartiles) [n]) by region (as per World Bank gross national income per capita classification) where the trials were conducted, and by types of result, funding and trials on medicines yielding US Food and Drug ...

Sixteen articles reported on novel medicines/new indications that were approved by the FDA. Fifteen out of 16 of these were published before or during the 6 month period after FDA approval date. Of these 16 articles, NEJM published 14 and Lancet published two papers. The latter two articles were non‐open access papers at the time of publication and 1 year later.

These results confirmed what other studies have reported with data obtained 1–2 years 5 or 2–9 6 years after publication. The median number of citations of articles reporting on novel medicines/new indications that were approved by the FDA influenced the number of citations of all medicine articles reporting positive results. Soon after publication, key trial results are widely cited likely due to their interest among clinicians, but this also suggests that articles could have been used by industry in their promotional activities during the product launch period, usually close to the FDA approval date. This could have been achieved through ordering high number of reprints. However, I did not contact journal editors since previous authors were unsuccessful in getting information about reprint numbers from the NEJM and JAMA 4, 5. Publication of key trial results before or soon after the product launch has been also described for the majority of 149 medicines approved by the FDA from 2005 to 2011 7.

This analysis demonstrated that 1 year after publication, industry‐funded trials are most cited and that the number of citations seems to be influenced by the launch of a novel product or new indication.

Competing Interests

The author has completed the Unified Competing Interest form at http://www.icmje.org/coi_disclosure.pdf (available on request from the corresponding author) and declares no support from any organization for the submitted work.

I thank Asbjørn Hrobjartsson MD, PhD, MPhil (Nordic Cochrane Centre, Rigshospitalet, Copenhagen, Denmark) for his comments on earlier versions of this paper and Ignacio Mahillo (Epidemiology Unit, Fundación Jiménez Díaz University Hospital, Universidad Autónoma de Madrid, Madrid, Spain), for conducting the statistical analysis. I also thank two anonymous reviewers for their comments and suggestions.

Funding

This work required no funding.

Supporting information

S1 Articles reporting on trial results totally or partially conducted in high‐income countries.

S2 Articles reporting on trial results conducted only in low‐ and midd‐income countries

Supporting info item

Notes

Dal‐Ré R. (2016) Number of citations 1 year after publication of trial results and their relation to medicines regulatory approval. Br J Clin Pharmacol, 81: 786–788. doi: 10.1111/bcp.12832.

References

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Articles from British Journal of Clinical Pharmacology are provided here courtesy of British Pharmacological Society