Systematic Reviews and other evidence synthesis projects

Recommeded:
Systematic Searches tutorials by Yale's Harvey Cushing/John Hay Whitney Medical Library.

This series provides guidance on the process of constructing a comprehensive search, from initial planning through grey lit and evaluating your search.

Bramer WM, de Jonge GB, Rethlefsen ML, Mast F, Kleijnen J. A systematic approach to searching: an efficient and complete method to develop literature searches. J Med Libr Assoc. 2018;106(4):531-541. doi:10.5195/jmla.2018.283. PMID: 30271302; PMCID: PMC6148622.

Boolean operators are the way that AND, OR, and NOT are used in databases.

If you search on...

• Myocardial Infarction AND stroke: All results will contain both myocardial infarction and stroke.
• Myocardial infarction OR stroke: Results may include just myocardial infarction, just stroke, or both.
• Myocardial infarction NOT stroke: Any records containing stroke will be excluded. Use very carefully! It is easy to accidentally remove relevant records.

Parentheses enable the creation of multi-part searches. They allow you to group your terms and control the order in which the database interprets them. With no parentheses, the database will process the terms from left to right.

• asthma AND (children OR pediatric): All results will contain both asthma and one or more of the synonyms.
• asthma AND children OR pediatric: Results may include asthma and children, just pediatric, or both sets of terms.

To formulate your research question, you identified the important concepts. These concepts will be the building blocks for your search.

A simplified version of how this works can be written as:
(Concept_A) AND (Concept_B) AND (Concept_C) AND (Concept_D)

For each concept, you will develop search terms. These will be joined by OR:
(TermA1 OR TermA2 OR...) AND (TermB1 OR TermB2 OR...) AND (TermC1 OR TermC2 OR...) AND (TermD1 OR TermD2 OR...)

A search concept table can help you organize the concepts and terms:
Blank concept table (Word doc) (PDF) developed by Cushing/Whitney Medical Library, Yale University

Example:

Concept tables for PubMed and PsycINFO for the research question Compare the effectiveness of acupuncture vs. hypnosis for smoking cessation

(“smoking cessation”[Mesh] OR “smoking/prevention and control”[Mesh] OR “smoking/therapy”[Mesh] OR “tobacco use disorder/prevention and control”[Mesh] OR “tobacco use disorder/therapy”[Mesh] OR smoking OR smoker*)
AND
(“hypnotherapy”[Mesh] OR hypnosis OR hypnotherapy)
AND
(“acupuncture therapy”[Mesh] OR acupuncture OR acupressure)

(DE "Smoking Cessation" OR  DE "Tobacco Smoking" OR DE "Tobacco Use Disorder" OR smoking OR smoker*)
AND
(DE "Hypnosis" OR DE "Hypnotherapy" OR DE "Autohypnosis" OR hypnosis OR hypnotherapy)
AND
(DE “Acupuncture” OR acupuncture OR acupressure)

Plan for success by keeping track of your searches!

1. Since systematic reviews and other evidence syntheses can take a long time, you may need to re-run your search close to publication in order to identify newer articles.
2. You will need to report, at a minimum, your search strategy in your article. The publisher may also require that you provide your full search string for at least one database.
3. You may wish to make all your search strings available as supplemental material. 

Document Your Search Strategies

• Save your exact search strategy for each database in a document such as MS Word or Google Docs.
• Record the date each database searched, years covered, any filters used, and number of hits retrieved.
• Record number of citations after de-duplication.

Tip: Save your search string for future use in personal account within each database (eg MyNCBI in PubMed, My Saved Searches in Web of Science, My EBSCOhost in CINAHL Plus).

Write Up Search Methods

• PRISMA for Searching: comprehensive guidance on how to report your search methods, including a checklist and full explanatory paper.
• Appendix 3: Documenting the Search Process in Systematic Reviews: CRD's guidance for undertaking reviews in health care. Centre for Reviews and Dissemination. January 2009.
• Searching for and Selecting Studies chapter of the Cochrane Handbook.

For additional models of search methodology reporting, refer to see other guidelines in Guides for Conducting Systematic Reviews.