Division of Epidemiology, JC School of Public Health and Primary Care, The Chinese University of Hong Kong, 4/F, School of Public Health Building, Prince of Wales Hospital, Shatin, New Territories, Hong Kong ; Shenzhen Municipal Key Laboratory for Health Risk Analysis, Shenzhen Research Institute, The Chinese University of Hong Kong, 10 Yuexing Erdao, Nanshan District, Shenzhen, Guangdong Province, China.
Evid Based Complement Alternat Med. 2013;2013:812179. doi: 10.1155/2013/812179. Epub 2013 Oct 8.
Systematic reviews (SRs) that fail to search non-English databases may miss relevant studies and cause selection bias. The bias may be particularly severe in SRs of traditional Chinese medicine (TCM) as most randomized controlled trials (RCT) in TCM are published and accessible only in Chinese. In this study we investigated how often Chinese databases were not searched in SRs of TCM, how many trials were missed, and whether a bias may occur if Chinese databases were not searched. We searched 5 databases in English and 3 in Chinese for RCTs of Chinese herbal medicine for coronary artery disease and found that 96.64% (115/119) eligible studies could be identified only from Chinese databases. In a random sample of 80 Cochrane reviews on TCM, we found that Chinese databases were only searched in 43 or 53.75%, in which almost all the included studies were identified from Chinese databases. We also compared SRs of the same topic and found that they may draw a different conclusion if Chinese databases were not searched. In conclusion, an overwhelmingly high percentage of eligible trials on TCM could only be identified in Chinese databases. Reviewers in TCM are suggested to search Chinese databases to reduce potential selection bias.
系统评价（SRs）如果未能搜索非英文数据库，则可能会遗漏相关研究并导致选择偏倚。这种偏倚在中医药（TCM）的 SR 中可能尤为严重，因为大多数中医药 RCT 仅以中文发表且可获取。在这项研究中，我们调查了在 TCM 的 SR 中未搜索中文数据库的频率、遗漏的试验数量，以及如果不搜索中文数据库是否可能发生偏倚。我们在英文数据库中搜索了 5 个数据库，在中文数据库中搜索了 3 个数据库，以寻找治疗冠心病的中草药 RCT，结果发现仅从中文数据库就可以确定 96.64%（115/119）的合格研究。在对 80 项中医药 Cochrane 综述的随机抽样中，我们发现只有 43 项或 53.75%搜索了中文数据库，其中几乎所有纳入的研究都来自中文数据库。我们还比较了相同主题的 SRs，如果不搜索中文数据库，它们可能会得出不同的结论。总之，只有中文数据库才能确定中医药的绝大多数合格试验。建议 TCM 的审查员搜索中文数据库以减少潜在的选择偏倚。
