Letters To The Editor
Copyright ©The Author(s) 2017. Published by Baishideng Publishing Group Inc. All rights reserved.
World J Gastroenterol. Oct 21, 2017; 23(39): 7198-7200
Published online Oct 21, 2017. doi: 10.3748/wjg.v23.i39.7198
Duplicate publication bias weakens the validity of meta-analysis of immunosuppression after transplantation
Cameron J Fairfield, Ewen M Harrison, Stephen J Wigmore
Cameron J Fairfield, Ewen M Harrison, Stephen J Wigmore, Department of Clinical Surgery, University of Edinburgh, Royal Infirmary of Edinburgh, Edinburgh EH16 4SA, United Kingdom
Author contributions: Fairfield CJ wrote this letter; Harrison EM and Wigmore SJ revised the letter.
Conflict-of-interest statement: The authors have no conflict of interest to report.
Open-Access: This article is an open-access article which was selected by an in-house editor and fully peer-reviewed by external reviewers. It is distributed in accordance with the Creative Commons Attribution Non Commercial (CC BY-NC 4.0) license, which permits others to distribute, remix, adapt, build upon this work non-commercially, and license their derivative works on different terms, provided the original work is properly cited and the use is non-commercial. See: http://creativecommons.org/licenses/by-nc/4.0/
Correspondence to: Cameron J Fairfield, MBChB, Department of Clinical Surgery, University of Edinburgh, Royal Infirmary of Edinburgh, 51 Little France Drive, Edinburgh EH16 4SA, United Kingdom. cameron.fairfield@nhs.net
Telephone: +44-131-2423614
Received: August 28, 2017
Peer-review started: August 29, 2017
First decision: September 13, 2017
Revised: September 15, 2017
Accepted: September 26, 2017
Article in press: September 26, 2017
Published online: October 21, 2017
Processing time: 53 Days and 19.4 Hours
Abstract

Duplicate publication can introduce significant bias into a meta-analysis if studies are inadvertently included more than once. Many studies are published in more than one journal to maximize readership and impact of the study findings. Inclusion of multiple publications of the same study within a meta-analysis affords inappropriate weight to the duplicated data if reports of the same study are not linked together. As studies which have positive findings are more likely to be published in multiple journals this leads to a potential overestimate of the benefits of an intervention. Recent advances in immunosuppression strategies following liver transplantation have led to many studies investigating immunosuppressive regimes including immunosuppression monotherapy. In this letter we focus on a recently published meta-analysis by Lan et al investigating studies assessing immunosuppression monotherapy for liver transplantation. The authors claim to have identified fourteen separate randomised studies investigating immunosuppression monotherapy. Seven of the references appear to relate to only three studies which have been subject to duplicate publication. Several similarities can be identified in each of the duplicate publications including similar authorship, identical immunosuppression regimes, identical dates of enrolment and citation of the original publication in the subsequent manuscripts. We discuss the evidence of the duplicate publication inclusion in the meta-analysis.

Keywords: Liver transplantation; Immunosuppression; Meta-analysis; Duplicate publication; Bias

Core tip: The purpose of this letter to the editor is to comment on the potential inclusion of duplicate publications within the meta-analysis titled: “Efficacy of immunosuppression monotherapy after liver transplantation: A meta-analysis”.