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Health Sciences Systematic Reviews

Guidance for conducting health sciences systematic reviews.

This pages includes guidance for developing a SR search strategy. See the Search Techniques page of this guide for information on using Boolean (AND and OR) and controlled vocabulary (e.g MeSH) for building the search. 

Search Process

PubMed and Ovid Medline are both MEDLINE. You only need to search one or the other. Not both. 

For an up-to-date SR with the most recent literature, the search should be repeated before the final analysis in order to capture literature that was published since the initial search.

A well designed SR search strategy should be sensitive enough to capture all relevant literature, which means that it will also retrieve a higher proportion of irrelevant results. It is normal for a SR search strategy to retrieve hundreds or thousands of results that do not meet the eligibility criteria. This part of the process. The SR team will identify the relevant articles during title & abstract screening and full-text review. 

Create Search Strategy from PICO Question

An SR search strategy must be broad enough to capture all relevant literature. A well-formulated PICO question will help you to identify the main concepts for your search strategy.

In most cases:

  • NOT all PICO elements should be used in the search. 
  • Include P (population or problem).
  • Include I (intervention).
  • Include C only for direct comparisons of two specific interventions.
  • Outcomes are usually NOT recommended to include in your search. 

In most databases, you are searching the title, abstract, keywords and other citation data. You are not searching the full-text of the articles.

Example 1: What are the effects of exercise and motor interventions on physical activity and motor outcomes during and after medical intervention on children and adolescents with Acute Lymphoblastic Leukemia?
PICO Example Include in search?
P (population) Children/Adolescents Yes 
P (problem) Acute Lymphoblastic Leukemia Yes
I Exercise and motor interventions in addition to medical intervention Yes
C Medical intervention without exercise and motor interventions No
O Physical activity and motor outcomes No
Combine with Boolean
Children AND Acute Lymphoblastic Leukemia AND Exercise 
In this example, we can combine P (population) AND P (problem) AND I (intervention) with the Boolean operator AND to find literature with all three concepts. The C (comparison) and O (outcomes) with be analyzed during the review process. 
Example 2: In patients with large choledocholithiasis, is endoscopic papillary dilation after sphincterotomy favored over sphincterotomy alone?
PICO Example Include in search?
P Patients with Choledocholithiasis Yes
I Endoscopic papillary dilation after Sphincterotomy Yes
C Sphincterotomy alone Yes
O Complete stone removal, adverse events, procedure time No
Combine with Boolean

Strategy 1: choledocholithiasis AND endoscopic papillary dilation AND sphincterotomy

Strategy 2: choledocholithiasis AND (endoscopic papillary dilation OR sphincterotomy)

Strategy 1: Use this strategy if you only want literature that directly compares the intervention and comparison in a single study.

Strategy 2: Use this strategy if you want literature that directly compares the intervention and comparison in a single study AND studies that examine sphincterotomy alone. Combining the intervention with the comparison with OR instead of AND broadens the search to find more literature.

The best strategy will depend on your question and the literature available to answer your question. 

Tip! Develop search strategy on a text document and then copy and paste into databases.

Synonyms and Relevant Terms for Each Concept

Gather synonyms and related terms for each concept. 

  • Types of synonyms and related words may include controlled vocabulary (e.g. MeSH), terms with similar meanings, alternative spellings, acronyms, both broad and specific terms, discipline-specific terms, and more. 
  • Find terms by viewing relevant literature, systematic reviews, and other information sources. Viewing the synonyms listed for controlled vocabulary (e.g. MESH entries) may help you locate relevant terms.

PubMed Search Example (this is just an example; a real SR search should include more terms for each concept)

LGBTQ AND Nursing Education AND Cultural Competency

Concept

Search Strategy [each concept should include a combination of keywords and controlled vocabulary (when applicable) AND may include a combination of OR and AND boolean operators]

LGBTQ

"Sexual and Gender Minorities"[Mesh]  OR "Homosexuality"[Mesh] OR "Bisexuality"[Mesh] OR "Transgender Persons"[Mesh] OR homosexuality OR lesbian OR gay OR bisexual OR transgender OR queer

Nursing Education

"Education, Nursing, Associate"[Mesh] OR "Education, Nursing, Baccalaureate"[Mesh] OR "Education, Nursing, Diploma Programs"[Mesh] OR "Education, Nursing, Graduate"[Mesh] OR "Students, Nursing"[Mesh] OR "Schools, Nursing"[Mesh] OR "Faculty, Nursing"[Mesh] OR Nursing education OR Nursing curriculum OR Nursing schools OR Nursing students OR Nursing faculty

Cultural Competency "Healthcare Disparities"[Mesh] OR "Cultural Competency"[Mesh] OR "Culturally Competent Care"[Mesh] OR competent OR competence OR competency OR competencies

Put it all together:

("Sexual and Gender Minorities"[Mesh]  OR "Homosexuality"[Mesh] OR "Bisexuality"[Mesh] OR "Transgender Persons"[Mesh] OR homosexuality OR lesbian OR gay OR bisexual OR transgender OR queer) AND ("Education, Nursing, Associate"[Mesh] OR "Education, Nursing, Baccalaureate"[Mesh] OR "Education, Nursing, Diploma Programs"[Mesh] OR "Education, Nursing, Graduate"[Mesh] OR "Students, Nursing"[Mesh] OR "Schools, Nursing"[Mesh] OR "Faculty, Nursing"[Mesh] OR Nursing education OR Nursing curriculum OR Nursing schools OR Nursing students OR Nursing faculty) AND ("Healthcare Disparities"[Mesh] OR "Cultural Competency"[Mesh] OR "Culturally Competent Care"[Mesh] OR competent OR competence OR competency OR competencies)

Refine Search

Some strategies for improving search results:

  1. View search strategies in high-quality published systematic reviews that include your search topics. You may be able to use these search strategies to help you start developing your search strategy. 
  2. Test search results to make sure that relevant articles that you've already identified are included. If your results do not include these articles, you should adjust your search strategy to include additional terms that will retrieve these articles. 
  3. View the most relevant articles to find additional relevant keywords and controlled vocabulary terms to include in your search. 
  4. Sort your results by my recent publication date. If there are thousands of articles that are way off topic, try to figure out which terms in your search strategy are retrieving the irrelevant results. Some common issues include: a broad MeSH term exploding to include very irrelevant terms, keywords that are too broad and used too commonly by authors, or unexpected results of truncation.

SR teams should search multiple databases. 

  • Each database has unique controlled vocabulary (when applicable), syntax, and search features.
  • For health sciences SRs, teams usually start by developing a search strategy for PubMed or Ovid Medline and then adjusting the search slightly to retrieve comparable results in the remaining databases. 
  • Depending on your research question, you may want to simultaneously develop the search strategy for at least two databases. For example, simultaneously developing the search strategy for PubMed and Embase can help you identify additional relevant keywords and controlled vocabulary terms for each search and reducing the amount of time for revising the strategies for each databases later. 

Peer review of SR searches can help identify errors in the search strategy. The peer review of SR searches can greatly improve the quality of the search and increase the number of relevant records found for inclusion in reviews, and thus improve the overall quality of the SR. 

Authors can use Peer Review of Electronic Search Strategies (PRESS) Guideline statement and checklist to review and revise their own strategies. Authors can also ask an experienced searcher, information specialist or librarian to review using the PRESS checklist. 

Search Methods & Appendix for Manuscript

PRISMA Checklist items related to search

# 6 Information Sources: Specify all databases, registers, websites, organisations, reference lists and other sources searched or consulted to identify studies. Specify the date when each source was last searched or consulted.

# 7 Search Strategy: Present the full search strategies for all databases, registers and websites, including any filters and limits used.