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Systematic Reviews: How to search the literature

Mae'r dudalen hon hefyd ar gael yn Gymraeg

Key steps to consider when formulating a search strategy

Step 1: Consider the different types of information available to you 

Step 2: Identify the specific resources that you will search

Step 3: Identify the key search terms that you will use

Step 4: Outline your plans for minimizing bias

Step 5: Plan how you are going to store and save the results of your search 

Dundar, Y., & Fleeman, N.  (2017). Developing my search strategy & applying inclusion criteria. In A. Boland, M.G. Cherry & R. Dickson (Eds.), Doing a systematic review: A student's guide (2nd ed., pp.37-59). Sage.

Search Filters

“Search filters are collections of search terms designed to retrieve selections of records. Search filters may be designed to retrieve records of research using a specific study design or by topic or by some other feature of the research question.

Filters may have a very specific focus or may be high level. Search filters may be designed to maximise sensitivity (or recall) or to maximise precision (and reduce the number of irrelevant records that need to be assessed for relevance).”

InterTASC Information Specialists’ Sub-Group. (2016). What is the ISSG filter resource? Retrieved June 10, 2016,

PICO - a tool for identifying your clinical question & search terms

Start considering your key search terms by identifying the key concepts in your research questions and then consider synonyms, related terms, different spellings, abbreviations, more specific and general terms that an author or authors may have used to discuss the topic.

The PICO tool Patient/Intervention/Comparison/Outcome can help you to frame your research question and identify concepts for your medical/clinical search.

 e.g. Hospital acquired infection

So your key terms could include; Hospital acquired infection/Cross infection


So your key search terms may include; handwashing/hand washing/hand-washing/hand hygiene

Other solutions

So your key search terms may include; alcohol rub/sanitizers/hand rub/hand gel

Reduced infection

So you may include reduction in your search. Although consider carefully as searching for articles that include hospital acquired infection and handwashing and other solutions you may find relevant material without the addition of reduced/reduction to your search.

Checklists & guidance for search strategies

Successful literature searching

The key points to a good search strategy are:

  • Defining your Keywords
  • Inclusion/exclusion criteria (ie: date of publication, language)
  • Where are you going to search? (databases, websites etc.)
  • Recording your results

Here are a few book chapters that can help you when it comes to developing your search strategy:

  • Aveyard, H. (2019). Doing a literature review in health and social care a practical guide (4th ed.). London: Open University Press. (Read Chapter 4 - How do I search for literature?)
  • Aveyard, H., Payne, S., & Preston, N. J. (2016). A post-graduate's guide to doing a literature review in health and social care. Maidenhead. Open University Press. (Read chapter 4 - How do I search for relevant literature?)
  • Boland, A., Cherry, M.G., & Dickson, R. (Eds.). (2014). Doing a systematic review: A student's guide. London: SAGE. (Read Chapter 3 - Developing my search strategy and applying inclusion criteria)
  • Booth, A., Papaioannou, D., & Sutton, A. (2012). Systematic approaches to a successful literature review. Los Angeles: Sage.
  • Greenhalgh, T. (2019). How to read a paper (6th ed.). Hoboken: John Wiley & Sons. (Read Chapter 2 - Searching the literature


  • Journal articles - Start with bibliographic databases such as PubMed, CINAHL, Web of Science
  • Grey Literature - This is basically anything not published in a journal, for example conference proceedings, Government documents, Reports from Organizations, try Google Scholar, Evidence Search, OpenGrey.

Talk to your Librarian about which sources of information may be relevant to your research question topic.

Keyword searching

Getting your keywords right is a very important part of the search process, the more literature you read on your  topic the more keywords and key terms you will come across.  At the beginning of your search you may only have a few keywords, with these you can conduct a scoping search (a brief, broad search) to get an overview of how much literature there is on your topic.  Based on your results you can then refine your keywords and rerun your search. Try using a tool such as PICO for your clinical questions.

Correct combination of your keywords using boolean operators (AND/OR/NOT) will be important.  We have created a research record form to help you to think about keywords for your search.  

Subject index searches

Some databases will also allow searching using a subject index, often called subject headings or thesaurus searches. For example Medical Subject Headings (MeSH) in PubMed/MEDLINE. Using subject heading searches is an advanced way of searching for literature and can provide a useful, focused set of results.  Each database will have a help page with further details.

For a systematic review you should be searching using both keywords and subject indexes (if available).

If you need help with identifying search terms for your search, identifying relevant sources of evidence to search or how to structure your search with boolean operators contact the Library team. We can advise you on these aspects of your search for your systematic review. Find our contact details on the Home page of this guide.