Medical Library, Erasmus MC, University Medical Centre Rotterdam, P.O. Box 2040, 3000 CS, Rotterdam, The Netherlands.
UBC Biomedical Branch Library, The University of British Columbia, Vancouver, Canada.
Syst Rev. 2018 Nov 20;7(1):200. doi: 10.1186/s13643-018-0864-9.
Researchers performing systematic reviews (SRs) must carefully consider the relevance of thousands of citations retrieved from bibliographic database searches, the majority of which will be excluded later on close inspection. Well-developed bibliographic searches are generally created with thesaurus or index terms in combination with keywords found in the title and/or abstract fields of citation records. Records in the bibliographic database Embase contain many more thesaurus terms than MEDLINE. Here, we aim to examine how limiting searches to major thesaurus terms (in MEDLINE called focus terms) in Embase and MEDLINE as well as limiting to words in the title and abstract fields of those databases affects the overall recall of SR searches.
To examine the impact of using search techniques aimed at higher precision, we analyzed previously completed SRs and focused our original searches to major thesaurus terms or terms in title and/or abstract only in Embase.com or in Embase.com and MEDLINE (Ovid) combined. We examined the total number of search results in both Embase and MEDLINE and checked whether included references were retrieved by these more focused approaches.
For 73 SRs, we limited Embase searches to major terms only while keeping the search in MEDLINE and other databases such as Web of Science as they were. The overall search yield (or total number of search results) was reduced by 8%. Six reviews (9%) lost more than 5% of the relevant references. Limiting Embase and MEDLINE to major thesaurus terms, the number of references was 13% lower. For 15% of the reviews, the loss of relevant references was more than 5%. Searching Embase for title and abstract caused a loss of more than 5% in 16 reviews (22%), while limiting Embase and MEDLINE that way this happened in 24 reviews (33%).
Of the four search options, two options substantially reduced the overall search yield. However, this also resulted in a greater chance of losing relevant references, even though many references were still found in other databases such as Web of Science.
进行系统评价（SR）的研究人员必须仔细考虑从文献数据库搜索中检索到的数千条引文的相关性，其中大多数引文在仔细检查后将被排除。经过良好开发的文献搜索通常使用词库或索引术语与引文记录的标题和/或摘要字段中找到的关键词相结合。Embase 文献数据库中的记录包含比 MEDLINE 更多的词库术语。在这里，我们旨在研究将搜索限制在 Embase 和 MEDLINE 中的主要词库术语（在 MEDLINE 中称为焦点术语）以及限制在这些数据库的标题和摘要字段中的单词如何影响 SR 搜索的整体召回率。
为了研究使用旨在提高精度的搜索技术的影响，我们分析了以前完成的 SR，并将我们的原始搜索集中在 Embase.com 中的主要词库术语或仅在标题和/或摘要中的术语上，或者集中在 Embase.com 和 MEDLINE（Ovid）组合中。我们检查了 Embase 和 MEDLINE 中的搜索结果总数，并检查了这些更集中的方法是否检索到了包含的参考文献。
对于 73 项 SR，我们仅将 Embase 搜索限制在主要术语上，同时保持 MEDLINE 和其他数据库（如 Web of Science）的搜索不变。整体搜索产出（或搜索结果总数）减少了 8%。有 6 项综述（9%）丢失了超过 5%的相关参考文献。将 Embase 和 MEDLINE 限制在主要词库术语范围内，参考文献数量减少了 13%。对于 15%的综述，丢失的相关参考文献超过 5%。在 16 项综述（22%）中，仅在 Embase 上搜索标题和摘要导致超过 5%的丢失，而通过这种方式限制 Embase 和 MEDLINE 则有 24 项综述（33%）发生这种情况。
在这四种搜索选项中，有两种选项大幅减少了整体搜索产出。然而，这也导致丢失相关参考文献的可能性增加，尽管在 Web of Science 等其他数据库中仍找到了许多参考文献。
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