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Gerstein Science Information Centre

Searching the Literature: A Guide to Comprehensive Searching in the Health Sciences

Students and researchers in the health sciences are often required to conduct comprehensive searches of the literature. Follow the steps in this guide to learn how this process works.

Why Search Multiple Databases?

Search a number of journal article databases in order to:

  • minimize bias
  • cast a wide net to try and retrieve as many studies as possible 
  • there is no single journal article database that indexes all the literature, not even MEDLINE

WHY? According to the Cochrane Handbook Section "Minimizing Bias":

Systematic reviews of interventions require a thorough, objective and reproducible search of a range of sources to identify as many relevant studies as possible (within resource limits). This is a major factor in distinguishing systematic reviews from traditional narrative reviews and helps to minimize bias and therefore assist in achieving reliable estimates of effects.

A search of MEDLINE alone is not considered adequate. A systematic review showed that only 30% - 80% of all known published randomized trials were identifiable using MEDLINE (depending on the area or specific question) (Dickersin 1994).

The same can be considered for any comprehensive search of the literature.

Health Science Database Ecosystem

There are two types of databases in the health sciences: subject databases and citation indexes.

Subject Databases for Health Sciences

PubMed vs OVID Medline

PubMed = Public Medline

MEDLINE is the largest component of PubMed (, the freely accessible online database of biomedical journal citations and abstracts created by the U.S. National Library of Medicine (NLM®). In addition to MEDLINE citations, PubMed also contains, among other items, in-process citations which provide a record for an article before it is indexed with MeSH and added to MEDLINE or converted to out-of-scope status. More information here

If you are searching Epub Ahead of Print, In-Process & Other Non-Indexed Citations, Ovid MEDLINE® Daily and Ovid MEDLINE® 1946-Present effectively, there is no reason to ALSO search PubMED. Ask your librarian for details. 

Key Citation Indexes

Health science research is often multidisciplinary. Below is a list of multidisciplinary databases to start you in the right path. You can also use these databases to conduct basic searches to 'scope' out a subject; quickly find seminal articles; and conduct bibliometrics research. We do not recommend searching these databases as part of a systematic review.