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Step 4 Search the literature

Develop a search strategy

The search strategy for a systematic review needs to be as comprehensive as possible in order to capture all studies relevant to the review question. 

The general process in developing a search strategy is:

  1. Identify synonyms and concepts related to the key concepts in your research question
  2. Identify the databases and other sources you need to search 
  3. Identify relevant database subject headings (e.g. MeSH - Medline, Emtree - Embase, etc) and apply to your search strategy
  4. Apply search techniques such as Boolean, Nesting, Phrase Searching, Truncation and Wildcards
  5. Consider if certain concepts/keywords require to be searched in particular database fields e.g. Title/Abstract
  6. Consider if certain database filters need to be applied in order to narrow the search e.g. publication dates, age, sex, article type, language etc.
  7. Test, review and amend search as required

A useful starting point can be to check the search strategies in published systematic reviews for examples of how searches are structured and assist in keyword development.

Your Liaison Librarian can provide you with assistance in developing search strategies.

Resources:

Documenting the search strategy

Systematic reviews require a meticulous documentation of their search strategy to enable a possible replication of their search in the future and a clear assessment of their quality. Most databases allow for the search history to saved which provides an exact record of the search.

Search details which must be recorded are;

  • Sources searched, such as:
    • Databases (including the platform) e.g. EBSCO (platform) PsycINFO (database).
    • Hand searching a record of the source (for example, Conference proceedings, journal title) and years searched must be kept
    • Grey Literature sources
    • Organisations or experts contacted.
  • The date the search was conducted and the period searched
  • Subject headings and keywords used
  • Search history, including the combination of terms and any restrictions applied such as Language.
  • Number of results retrieved 
  • Total number of records retrieved
  • Duplicates identified

The numbers of search results are documented using the PRISMA Flow Diagram.

Resources:

Managing search results

It is important to establish a method for managing the search results retrieved via your search strategy.

Reference management software such as EndNote are commonly used in systematic reviews for exporting all search results from final database searches so that the studies can be screened and inclusion/exclusion criteria applied.

Covidence is also a widely used tool for managing systematic reviews (not a free tool).

Resources:

Databases

Identify the relevant databases for your review. Your Liaison Librarian can advise on which databases should be searched and on developing search strategies.

Below are some of the most important Health databases:

Study registers

Grey literature

Literature that is NOT published in traditional sources such as books and journals is referred to as “Grey literature”.

Conference proceedings and theses are the most common types of Grey literature in the academic context, but examples also include technical and research reports, government publications, policy papers, annual reports, fact sheets, maps, geological surveys and statistics.

Sources of grey literature

Dissertations and Theses

Conference abstracts & proceedings

  • Directory of Published Papers : contains material from more than 40,000 conferences & symposia, across Science/Technology, Medical/Life Sciences, Pollution Control/Ecology, Social Sciences/Humanities.

Australian sources of grey literature

 International sources of grey literature

  • World Health Organization
  • The Grey Literature Report: The report is a bimonthly publication of The New York Academy of Medicine Library alerting readers to new grey literature publications in health services research and selected public health topics.
  • Grey Matters: a practical search tool for evidence-based medicine: Published by The Canadian Agency for Drugs and Technologies in Health (CADTH). Provides details on where to locate grey literature in Australia and other countries.
  • OpenGrey: System for Information on Grey Literature in Europe, is your open access to 700.000 bibliographical references of grey literature (paper) produced in Europe and allows you to export records and locate the documents.
  • National Technical Information Service (U.S.): The National Technical Information Service is the largest central resource for U.S. government-funded scientific, technical, engineering, and business related information.
  • OAIster: a union catalog of millions of records representing open access resources including theses, technical reports and research papers.
  • Google: A search of Google using keywords and the advanced search functionality allows for limiting searches to specific domains such as government or research web sites. This can be useful for tracking down grey literature.
  • PsychEXTRACovers technical, annual and government reports, conference papers, newsletters, magazines, newspapers and consumer brochures in  psychology.
  • CogPrints: A self-archive for papers in any area of Psychology, Neuroscience, and Linguistics, and many areas of Computer Science.
  • Mednar: A federated search engine of peer-reviewed medical resources. 
  • OpenDOAR - Directory of Open Access Repositories

Hand searching

Hand searching is the manual examination of resources which are not indexed electronically, such as special issues of journals or conference proceedings.