Design and implementation of Metta, a metasearch engine for biomedical literature retrieval intended for systematic reviewers

Neil R. Smalheiser, Can Lin, Lifeng Jia, Yu Jiang, Aaron M. Cohen, Clement Yu, John M. Davis, Clive E. Adams, Marian S. McDonagh, Weiyi Meng

Research output: Contribution to journalArticlepeer-review

19 Scopus citations


Background: Individuals and groups who write systematic reviews and meta-analyses in evidence-based medicine regularly carry out literature searches across multiple search engines linked to different bibliographic databases, and thus have an urgent need for a suitable metasearch engine to save time spent on repeated searches and to remove duplicate publications from initial consideration. Unlike general users who generally carry out searches to find a few highly relevant (or highly recent) articles, systematic reviewers seek to obtain a comprehensive set of articles on a given topic, satisfying specific criteria. This creates special requirements and challenges for metasearch engine design and implementation. Methods: We created a federated search tool that is connected to five databases: PubMed, EMBASE, CINAHL, PsycINFO, and the Cochrane Central Register of Controlled Trials. Retrieved bibliographic records were shown online optionally, results could be de-duplicated and exported in both BibTex and XML format. Results: The query interface was extensively modified in response to feedback from users within our team. Besides a general search track and one focused on human-related articles, we also added search tracks optimized to identify case reports and systematic reviews. Although users could modify preset search options, they were rarely if ever altered in practice. Up to several thousand retrieved records could be exported within a few minutes. De-duplication of records returned from multiple databases was carried out in a prioritized fashion that favored retaining citations returned from PubMed. Conclusions: Systematic reviewers are used to formulating complex queries using strategies and search tags that are specific for individual databases. Metta offers a different approach that may save substantial time but which requires modification of current search strategies and better indexing of randomized controlled trial articles. We envision Metta as one piece of a multi-tool pipeline that will assist systematic reviewers in retrieving, filtering and assessing publications. As such, Metta may find wide utility for anyone who is carrying out a comprehensive search of the biomedical literature.

Original languageEnglish (US)
Article number1
JournalHealth Information Science and Systems
Issue number1
StatePublished - Jan 10 2014


  • Bibliometrics
  • Evidence-based medicine
  • Information retrieval
  • Medical informatics
  • Meta-analysis
  • Metasearch engine
  • Systematic reviews

ASJC Scopus subject areas

  • Health Informatics
  • Health Information Management
  • Information Systems


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