RESUMEN
OBJECTIVE: Duplicate publication has a negative influence on science and publishing communities. We found duplicate publication cases in the field of Kampo (traditional Japanese herbal medicine) while compiling the Evidence Reports of Kampo Treatment (EKAT) 2009 published by the Special Committee for Evidence-based Medicine (EBM), the Japan Society for Oriental Medicine (JSOM). Therefore, we checked the articles that appeared in the EKAT 2009 and analyzed how duplicate publication occurred. METHODS: The EKAT 2009 contains structured abstracts of 320 randomized controlled trial studies. We checked 384 articles referred to by the structured abstracts to identify duplicate publications according to the following criteria: hypothesis and results are the same; the authors are in common; no description as to a secondary publication is offered; no cross-references to related papers. RESULTS: Eleven articles that appeared in the EKAT 2009 were identified as duplicate publications. These articles showed four duplicate patterns: reproducing an already published article with the same sample data and results (n=3); adding new sample data with the same results (n=1); reporting part of the preliminary sample with the same results (n=1); translating an original article into another language (n=6). CONCLUSION: Among the 11 duplicate publications in the EKAT 2009, we discovered 4 duplicate patterns. These patterns reflect Japanese researchers' behavior that leads to the production of duplicate publications: the authors complete a previous article and submit it to a more prestigious journal; translate an original English article for Japanese physicians without referring to the original paper. To raise the awareness of duplicate publication among researchers, the understanding of publication ethics is essential.