Systematic Literature Reviews at Master's Level: Step 3: Develop your search strategy

Getting started writing your search

Develop your research question (see Step 1) using one of the tools such as PICO or PCC. This gives you the search concepts - the ideas that make up your question.

• Take those concepts and put them into a format that can be used in the databases
• Write this initial search in one of the databases such as Medline
• Remember to save your search strategy as you go along

Identify search terms for each concept

• Keywords (free-text terms used in titles and abstracts)

  • Synonyms and alternative spellings are necessary

• Subject Heading terms such as Medline's MeSH or Embase's Emtree

Specify which fields to search for keywords

• Title, Abstract and Author Keywords are the most commonly used
  • (myocardial infarction).ti,ab,kf.

Use truncation and phrase searching

• Truncation (usually *) finds multiple word endings:
  • rehab* finds rehabilitation, rehabilitate, rehabilitated
• Phrases : Quote marks (" ") search for the words as a phrase
  • "delayed prescriptions"

Use boolean operators

• OR to combine synonyms or related terms
  • myocardial infarction OR heart attack​​
• AND to combine different concepts
  • myocardial infarctionAND rehabilitation​
• NOT to exclude terms (use cautiously)
  • cancer NOT breast
• Proximity to bring search words closer but not as a phrase. The words are usually in any order and within a number of words of each other
  • cancer ADJ3 breast  will find breast cancer as well as cancer of the breast (ADJ is used in Medline)

Group with brackets

• (teenager OR adolescent) AND (depression OR mood disorder)

Use subject headings

Articles are indexed on databases using subject headings which are fixed or controlled lists of keywords which group together articles on the same topic regardless of wording

• Look up your topic word to find the subject heading
  • In MEDLINE, the MeSH term for heart attack is Myocardial Infarction/
• 'Explode' the subject heading to include any narrower terms
  • exp Myocardial Infarction/ will include Shock, Cardiogenic/ etc.

Combine subject headings with free-text

e.g. for Ovid Medline:

1. exp myocardial infarction/

2. (myocardial infarction* OR heart attack*).ti,ab,kf

3. 1 OR 2

4. rehabilitation/

5. rehab*.ti,ab,kf.

6. 4 or 5

7. 3 AND 6

Use limits carefully

Databases allow you to limit by:

• Language

• Publication year

• Study type (e.g., human studies, randomised controlled trials)

⚠️ Be cautious — using limits can unintentionally exclude relevant studies

Video tutorials

Have a look at our short videos

Document your search

You need to document your search. Good documentation includes:

• Databases searched
  • e.g. MEDLINE via Ovid
• Date of search
• Complete search strategy
  • including subject headings and keywords
• Any limits or filters used

This is essential for transparency and reproducibility — even if you're not doing a full systematic review. You will need this information to create your PRISMA flowchart.

Save the searches as you do them

After each time you edit your search, you should save the changes.

Start a draft search strategy (Word document or Excel spreadsheet).

• In Ovid
  • Click "Share Search History"
  • Click "Copy Search History Link"
  • Paste into your draft document
  • Repeat for "Copy Search History Details". This will note the number of results also.
     
• In CINAHL
  • Click Recent Activity on the left
  • In the top (latest) line, click the 3 vertical dots and click "Add to project"
  • 
  • Create a new project or use an existing one, as appropriate
  • Click Project on the left menu
  • Click on the project name in the list
  • Click on the Searches tab
  • Copy the search as seen, and paste into your draft document
    e.g. (XB rehab* OR MH "Rehabilitation+") AND (XB ((myocardial infarction* OR heart attack*)) OR MH "Myocardial Infarction")
  • Note also the number of results found in this search

Download templates

Why test your search?

Testing your search helps catch mistakes, improve its quality, and reduces the chance of missing studies or getting too many irrelevant ones.

How to test your search

There are 4 stages to testing your search. Take the search you have written and 

1. Run your search in your first database, e.g. Medline
2. Review the results
3. Make changes to your search as needed
4. Repeat as needed

It's important to get this right so spend some time on this stage.

1. Run your search

Take your search and enter the search lines and commands into your chosen database e.g. Medline (OVID) 

1. exp myocardial infarction/
2. (myocardial infarction* or heart attack*).ti,ab,kf.
3. 1 or 2
4. rehabilitation/
5. rehab*.ti,ab,kf.
6. 4 or 5
7. exp analgesia/
8. (analgesia or (pain adj2 (relief or manag*))).ti,ab,kf.
9. 7 or 8
10. 3 and 6 and 9

2. Review your search

Look at the search results list that this search generates. 

• Are there enough results?
  • do you need to add more synonyms?
  • do you need to remove a search concept?
• Are there too many results?
  • are the search terms picking up irrelevant results?
    • Abbreviations can cause problems e.g. AI can mean artificial intelligence or artificial insemination
  • do you need to add another search concept?
• Test that the results contain any relevant papers you have identified in your preliminary searches 
  • search for the title of the paper
  • If the paper is found, take that result and the final line of your main search and join these with AND
    1. exp myocardial infarction/
    2. (myocardial infarction* or heart attack*).ti,ab,kf.
    3. 1 or 2
    4. rehabilitation/
    5. rehab*.ti,ab,kf.
    6. 4 or 5
    7. exp analgesia/
    8. (analgesia or (pain adj2 (relief or manag*))).ti,ab,kf.
    9. 7 or 8
    10. 3 and 6 and 9
    11. ("Chest pain self-management training for patients with coronary artery disease").ti.
    12. 10 AND 11

3. Change your search

If you have discovered a problem with your search, make changes to amend your search

• Add new synonyms
• remove troublesome search words
• Add new concepts

4. Repeat as needed

You may spend some time adjusting your search.

• It's important to keep going until you are content with your search
• Ask for help from a fellow student or your supervisor to review your search
• If you are still not getting good results, ask for help from your subject librarian

Start with one database search

After testing your search, you will have a detailed search strategy in one database (often Ovid MEDLINE). Next you will need to translate that search to your other chosen databases.

Translate subject headings

Make sure that you are using the correct subject headings. A database will use its own list of subject headings. Look up the equivalent subject headings in the new database:

• MEDLINE MeSH
• Embase Emtree
• CINAHL Headings
• PsycINFO APA Thesaurus

Some databases don't use a thesaurus at all. Use free text searching only in those databases.

• Web of Science
• Scopus

Adapt the database commands 

Make sure that you are using the correct commands. Databases use different commands for specifying fields e.g.:

Subject headings in:

• Ovid (Medline, Embase)
  • exp myocardial infarction/
• Ebsco (CINAHL)
  • (MH "Myocardial Infarction+") 

Free text searching in:

• Ovid (Medline, Embase) 
  • (myocardial infarction).ti.ab.kf
• Ebsco (CINAHL)
  • (XB ("myocardial infarction")

Proximity searching in:

• Ovid (Medline, Embase) 
  • (breast ADJ3 cancer).ti.ab.kf
• Ebsco (CINAHL)
  • (XB (breast N3 cancer)

Maintain the meaning of your search terms

Make sure that you are keeping the same meaning across databases:

• Use the equivalent fields
• Use the equivalent subject headings (if available)
• Add any new terms you find to previous database searches
  • if you find a new search word you need to add it to the previous search as well as this one

Use translation tools (optional)

The process can be complicated. Some tools can help with translation:

• Polyglot Search Translator (from the Institute for Evidence-Based Healthcare):
  https://polyglot.sr-accelerator.com/
• MeSH on Demand: Suggests MeSH terms based on text input 
  https://meshb.nlm.nih.gov/MeSHonDemand

⚠️ Use these tools carefully—manual checking is still essential!

Test and adjust

As you did for your initial search, test and adjust your search to make sure you are capturing relevant papers.

Video tutorials

Have a look at our short videos

Run the search
Take each database in turn. Copy and paste your searches for each database from your draft document or use your saved links to run your search.

Select results to export
For Ovid (Embase, Medline etc.)

• In the results list, click the All checkbox
  • If your list is over 2000 results, use the Range box and enter 1-2000
• Click Export
• Change Format from PDF to RIS 
  • RIS works in all reference managers and systematic review software so is the most flexible option
• Change Fields to Complete Reference
  • you might need all this data so take it now
• Click Export
• Save the file with a user friendly name and in a sensible place
• Repeat for larger searches
  • enter 2001-4000 in the Range box etc.

For Ebsco (CINAHL etc.)

• In the results list, click the drop down arrow next to the Tick All box
  
• Click Export results (up to 25000) 
• Enter your email address
• Click RIS
• Click Send

Grey literature

What is grey literature?

Grey literature refers to materials published or made available by organisations or individuals, rather than through commercial publishers. It is often defined by what it is not, meaning anything not controlled by the traditional, usually peer-reviewed, academic publishing market.

Some examples of grey literature

Reports produced by professional associations, government bodies, charities etc., discussion papers, media sources such as blogs, webpages, news reports, documentaries.

Why is it important?

It is part of the total of available evidence. Including grey literature can reduce bias, especially publication bias, which favours positive studies. Unpublished studies may have smaller sample sizes or be of lower quality, but their exclusion can lead to an overestimation of treatment effects.

• It is often the best available evidence when formal research is lacking.
• It complements published literature and helps communicate findings to a wider audience.

Sources - policy documents

Sources - grey literature-specific

Video tutorial

Watch our short video