Abstract
With the increasing use of meta-analysis, duplicate publication of original research is particularly problematic. Duplicate publication can result in an inappropriate weighting of the study results. The purpose of our study was to assess the incidence and characteristics of duplicate publications in Korea, and to estimate the impact of duplicate publication on meta-analyses. The meta-analysis literature written by Korean authors was searched using the online search engines PubMed, KMbase, and KoreaMed. Duplication patterns were classified into the following 4 combinations: identical samples and identical outcomes (copy), identical samples and different outcomes (fragmentation), increased samples and identical outcomes (imalas), and decreased samples and identical outcomes (disaggregation). To estimate the multiple publication bias, we performed a meta-analysis with and without duplicated data. We estimated that 6 (6.9%) of the 86 analyzed meta-analyses included duplicate publications, and 6 of the 1,194 articles (0.5%) used in the meta-analyses were duplicate publications. In this study, duplicate publications were usually due to disaggregation and overlapping (imalas) publications. Of 6 duplicated articles, 1 was considered a copy (16.6%); 1, a fragmentation (16.6%); 2, imalas (33.3%); and 2, disaggregations (33.3%). There was an increase in the mean effect size and fail-safe number with duplicated data. Our study found only 6 instances of duplicate publication after analyzing 1,194 articles used in meta-analyses written by Korean authors. However, 6.9% of the meta-analyses included duplicate publications. Our findings suggest that meta-analyses should be interpreted cautiously, taking into account the possibility of duplicated studies.
Highlights
Over the past few decades, there has been an explosive increase in biomedical publications, and the practice of duplicate publication is sometimes problematic in the scientific medical community
Systematic search and study selection The meta-analysis literature written by Korean authors was searched using the online search engines PubMed, KMbase, and KoreaMed
Our study suggests that 6.9% of the meta-analysis articles that were written by Korean authors included duplicate publications
Summary
Over the past few decades, there has been an explosive increase in biomedical publications, and the practice of duplicate publication is sometimes problematic in the scientific medical community. According to the International Committee of Medical Journal Editors, duplicate (or redundant) publication can be defined as “the publication of an article that overlaps substantially with one already published in print or electronic media” (2013). Duplicate publication is unethical because it is wasteful of the time, effort, and resources of journals, editors, peer reviewers, readers, libraries, and electronic databases; it delays the publication time for papers from other researchers (Leopold 2013). In Korea, Kim et al (Kim et al 2008) reported that 27 (5.93%) of 455 articles were duplicated
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