Systematic Reviews and other evidence synthesis projects

For an introduction to or refresher on conducting complex searches, visit this series of tutorials on systematic searching by Yale's Harvey Cushing/John Hay Whitney Medical Library.

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 search process!

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. 

Tracking your search process can be done using a word-processing document, such as in Microsoft Word or Google Docs, to record your full search strings, the date you ran them, and any filters you applied.

You can also use the PRISMA-S checklist to keep track of the information that you should record. The checklist is described in depth in PRISMA-S: an extension to the PRISMA Statement for Reporting Literature Searches in Systematic Reviews.