Epidemiology: Electronic bibliographic databases and their limitations
In an aged of evidence based medicine, being able to search for relevant research to answer a question is crucial to both scientists and clinicians. At the same time, computers and particularly the internet have revolutionised medical publishing. With thousands of research articles being published each year, bibliographic databases provide a way to search the archives of multiple journals from across the world.
A bibliographic database is a repository of bibliographic or publication records. It provides an index of journal articles from multiple journals, and includes citations, abstracts and often a link to the full text. Databases are usually held electronically, so they can be updated regularly, either on a CD-ROM or increasingly online.
The Medline database
Medline is perhaps the best known bibliographic database, and can be accessed free of charge via several online portals including PubMed. It is compiled by the National Library of Medicine of the United States and is thought to include around 30-40% of the 10 million biomedical articles that have been published.1 Medline currently, indexes citations from approximately 5,200 biomedical journals in 37 languages. 670,000 references were added in 2007 alone.2
Articles can be traced in two ways: by terms including words in the title, abstract, authors' names, and institution or by a restricted thesaurus of medical titles, known as medical subject heading (MeSH) terms.1
The best way to learn about bibliographic databases is to use them. Trisha Greenhalgh’s article1 includes several worked examples that can be replicated in Medline.
Embase, published by Elsevier, is a smaller biomedical database of about 12 million records from 1974 to the present.3 There is about a 40% overlap in coverage between it and Medline. Embase is more up-to-date, has a European slant and is more comprehensive on drug literature and alternative therapies.
Other biomedical databases include:1
- American Medical Association Journals
- Cochrane Library
- Science Citation Index
Limitations of electronic databases
- Databases may not yet contain the most recent references
- Search results from bibliographic databases depend on the search strategy used
- Obtaining a comprehensive selection of references can involve searching several databases because their coverage varies
- Most databases only include published articles; it is necessary to search separately for grey literature
- Greenhalgh, T. How to read a paper: The Medline database BMJ 1997 315: 180-183
- http://www.nlm.nih.gov/pubs/factsheets/medline.html - Accessed 23/01/09
- http://www.elsevier.com/wps/find/bibliographicdatabasedescription.cws_ho... – Accessed 23/01/09
© Helen Barratt 2009