Unpublished systematic reviews and financial support: a meta-epidemiological study




Poster session 4


Tuesday 25 October 2016 - 15:30 to 16:00


All authors in correct order:

Tsujimoto H1, Tsujimoto Y2, Kataoka Y3
1 Department of Cell Growth and Differentiation, Graduate School of Medicine, Kyoto University, Japan
2 Department of Healthcare Epidemiology, Graduate School of Medicine and Public Health, Kyoto University, Japan
3 Hospital Care Research Unit, Hyogo Amagasaki General Medical Center, Japan
Presenting author and contact person

Presenting author:

Hiraku Tsujimoto

Contact person:

Abstract text
Background: The international prospective register of systematic reviews (PROSPERO) was launched in February 2011 to reduce publication bias of systematic reviews (SRs). A questionnaire survey sent to SR researchers in 2005 indicated the existence of unpublished SRs and potential influence of lack of funding on non-publication. Before PROSPERO, there were no specific international registration systems for SRs; no-one could survey this feature of unpublished SRs. PROSPERO had over 13000 records in April 2016. Here, we investigate the publication status of PROSPERO-registered SRs and the relationship of financial support to publication.

Objectives: To investigate the proportion of unpublished SRs to registered protocols and the influence of financial support on their publication

Methods: We investigated current publication status of registered SRs in the first year of the PROSPERO launch. We also searched for published SRs not reflected in PROSPERO publication status using Google and Google scholar. The association between publication and existence of funding or conflicts of interest were investigated using logistic regression analysis.

Results: We identified 326 records in PROSPERO from February 2011 to February 2012. The records did not include Cochrane protocols. Among them 100 (31%) SRs were not published in April 2016. Funding for SRs (odds ratio (OR) 1.84 (95% confidence interval (CI) 1.13 to 3.00)) related to the publication of SRs. We did not find significant effects of author-reported conflicts of interest on publication (OR 2.11 (95% CI 0.69 to 6.42)). We found that 26 records were not published, although the authors reported the completion of the reviews in PROSPERO.

Conclusions: We found a non-negligible proportion of unpublished SRs more than 50 months after their protocol registration. Although we did not investigate the potential effect of publication bias (effect of clinical significance of each SR results), these unpublished SRs may produce it. Lack of funding may hinder publication of SRs.