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Health Sciences Literature Reviews

Overview of the library's service and a listing of resources to get started with your review.

The Search Process for Evidence Syntheses

The goal of evidence synthesis searches is to identify all relevant studies on a topic. Therefore, these searches are typically quite extensive. It is necessary, however, to strike a balance between striving for comprehensiveness and maintaining relevance when developing a search strategy. Increasing the comprehensiveness (or sensitivity) of a search will reduce its precision and will retrieve more non-relevant articles.

It is also important to document your search strategy in order to increase transparency and the reproducibility of your searches.

Guidance for Comprehensive Searching and Documentation

Preliminary search

Look for existing evidence syntheses or protocols on your topic (or a similar topic). This will allow you to:

  1. Learn if any existing evidence syntheses already exist on your research question. If they do, your team can either reconsider your research question or the type of review.
  2. Find comprehensive search strategies or protocols on a similar topic.

Below are some good places to start:

Next, do a quick search in PubMed (or another relevant academic research database) to get a better sense of how much relevant literature is available on your research question for you to conduct your evidence synthesis. 

At this stage, you can save a few of the relevant studies you know you want to include in your final review (between 3 and 10), which will come in handy as you create and test your final comprehensive search strategy.

Creating your Comprehensive Search Strategy

The goal is to maximize recall and precision while keeping results manageable. Recall (sensitivity) is defined as the number of relevant reports identified divided by the total number of relevant reports in existence. Precision (specificity) is defined as the number of relevant reports identified divided by the total number of reports identified.  

Things to consider when creating a comprehensive search:   

  • All concepts are included in the search strategy
  • ​All appropriate subject headings are used
  • Appropriate use of explosion
  • Appropriate use of subheadings and floating subheadings
  • Use of natural language (text words) in addition to controlled vocabulary terms (e.g., MeSH terms)
  • Use of appropriate synonyms, acronyms, etc.
  • Truncation and spelling variation as appropriate
  • Appropriate use of limits such as language, years, etc.
  • Field searching, publication type, author, etc.
  • Boolean operators used appropriately
  • Line errors: when searches are combined using line numbers, be sure the numbers refer to the searches intended
  • Check indexing of relevant articles
  • Search strategy adapted as needed for multiple databases