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World J Meta-Anal. Nov 26, 2013; 1(3): 97-101
Published online Nov 26, 2013. doi: 10.13105/wjma.v1.i3.97
Duplicates in systematic reviews: A critical, but often neglected issue
Xing-Shun Qi, Ming Bai, Zhi-Ping Yang, Wei-Rong Ren
Xing-Shun Qi, Ming Bai, Zhi-Ping Yang, Wei-Rong Ren, Xijing Hospital of Digestive Diseases, Fourth Military Medical University, Xi’an 710032, Shaanxi Province, China
Xing-Shun Qi, Department of Gastroenterology, No. 463 Hospital of Chinese PLA, Shenyang 110045, Liaoning Province, China
Author contributions: Qi XS, Bai M, Yang ZP and Ren WR performed the literature search; Qi XS wrote the first draft; Bai M, Yang ZP and Ren WR revised the manuscript.
Correspondence to: Xing-Shun Qi, MD, Xijing Hospital of Digestive Diseases, Fourth Military Medical University, No. 27 West Changle Road, Xi’an 710032, Shaanxi Province, China. xingshunqi@126.com
Telephone: +86-29-84771537 Fax: +86-29-82539041
Received: August 27, 2013
Revised: October 15, 2013
Accepted: November 20, 2013
Published online: November 26, 2013
Processing time: 113 Days and 21.1 Hours
Abstract

The number of systematic reviews is gradually increasing over time. Also, the methods to perform a systematic review are being improved. However, little attention has been paid for the issue regarding how to find duplicates in systematic reviews. On the basis of the survey and systematic reviews by our team and others, we review the prevalence, significance and classification of duplicates and the method to find duplicates in a systematic review. Notably, although a preliminary method to find duplicates is established, its usefulness and convenience need to be further confirmed.

Keywords: Duplicates; Systematic review; Method; Prevalence; Significance

Core tip: Finding duplicates is an indispensable step in a systematic review. The prevalence of duplicates ranges from 7% to 25%, as three different databases were searched (PubMed, EMBASE, Cochrane library). Until now, few studies have reported the detailed information regarding how to find duplicates. A preliminary method to find duplicates is established, but its usefulness and convenience need to be further confirmed.