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EPIB 619 Systematic Reviews & Meta-Analyses

Systematic searching

Systematic searching

Knowledge syntheses involve systematically searching the literature. For example,

Systematic reviews of interventions require a thorough, objective and reproducible search of a range of sources to identify as many relevant studies as possible (within resource limits). This is a major factor in distinguishing systematic reviews from traditional narrative reviews (...)

Higgins JPT, Green S (editors). Cochrane Handbook for Systematic Reviews of Interventions Version 5.1.0. The Cochrane
Collaboration, 2011. Available from http://handbook-5-1.cochrane.org/.

Systematic searching is:

  • Thorough: It involves searching more than one database and using a combination of textwords plus subject headings (the latter when available) to identify relevant literature. It also involves using supplementary search methods in addition to database searching
  • Objective: Search terms include variations in terminology and the searcher should avoid biasing the results of the search through the selection of search terms
  • Reproducible: The searcher is careful to record all the details of the search, including the database and platform with dates of coverage (may differ based on institutional subscriptions), the search strategy as executed, and the date the searches were run

Developing and running the database searches

Developing and running the database searches

We recommend developing the search strategy in one database before translating the search strategy to the other selected databases: This will make it easier to keep track of things. If you subsequently find terms in the other selected databases, you can then go back and add them to the searches that have already been developed.

It is recommended that you have your search strategy peer reviewed. For peer review criteria and critical appraisal search strategies, consult:

  • McGowan J, Sampson M, Salzwedel DM, Cogo E, Foerster V, Lefebvre C. PRESS Peer Review of Electronic Search Strategies: 2015 Guideline Statement. J Clin Epidemiol. 2016 Jul;75:40-6. doi: 10.1016/j.jclinepi.2016.01.021. Epub 2016 Mar 19. PubMed PMID: 27005575.

We also recommend running all the searches on the same day to make it easier to document the date in your manuscript. 

Once you have your searches developed and you are ready to run them, you can the export the records from each database to an EndNote library, which you will keep for your files.

Example of a worksheet

Worksheet for search terms

Keep track of the terms you will be using in your search strategy in whatever way works best for you. Below, we provide an example of a worksheet that can be used for this purpose. Depending on your research question, the list of terms can get quite long and can be difficult to manage if you are not recording them as you are finding them.

Subject headings - definition

Subject headings: Definition

A subject heading is an assigned word or phrase used in some databases to uniformly describe a concept. Searching using this standardized word or phrase, instead of keywords, means you do not need to worry about synonyms and spelling variations.

Example: The subject heading for cancer in MEDLINE (via PubMed) is the MeSH term Neoplasms. This means that all articles selected for indexing in MEDLINE that are about cancer at a general level will be tagged or indexed with this subject heading, or if the article is about a specfic cancer like breast cancer, with a narrower term (note: there is a time delay between the addition of records to MEDLINE and their indexing).

Tutorials

We recommend the following resources if you would like to explore subject headings in more detail:

Keywords - definition

Keywords: Definition

Keyword (or textword) searching is when we search for words which we expect to find in the title, abstract, or author-defined terms of relevant articles; it is how we typically interrogate web search engines. Draw up a list of words or phrases related to each concept in your research question. When using this technique, you will need to be aware of synonyms and spelling variations.

Example: Keywords (or textwords) for cancer can include cancer / cancers / cancerous / neoplasm / neoplasms / neoplastic / tumor / tumors / tumour / tumours etc.

Database and platform cheat sheet

Database and platform cheat sheet: PubMed, Ovid Online, Web of Science

 

PubMed (MEDLINE)

 

Ovid Online

 

Web of Science
Command Search

Subject headings

 

MeSH (Medical Subject Headings)

 

MEDLINE: MeSH
Embase: EMTREE

Avoid cross-searching databases so that you can take advantage of the subject headings, if applicable

NA (includes Keywords Plus, searched by default)


TS=("mycobacterium tuberculosis")

Searching subject headings

"MeSH term"[mesh]


Includes narrower terms by default
"Tuberculosis"[mesh]

exp subject heading/


"Explode" to include narrower terms
exp tuberculosis/

NA

 

Searching major subject headings

"MeSH term"[majr]

Retrieves records in which the MeSH concept is considered a central topic of the article

"Tuberculosis"[majr]

exp *subject heading/

Retrieves records in which the subject heading is considered a central topic of the article

exp *tuberculosis/

 

Searching title/abstract

 

term[tiab]


tb[tiab]

Searches author keywords too

term.ti,ab


tb.ti,ab

Does not search author keywords in Ovid MEDLINE; to search author keywords too, use:

term.ti,ab,kf

tb.ti,ab,kf

 

Searching title terms

 

term[ti]


obesity[ti]

term.ti.


obesity.ti.

TI=(term)


TI=(obesity)

Searching title/abstract/
entry terms

term[tw]


infliximab[tw]

term.mp.


infliximab.mp.

TS=(term)


TS=(infliximab)

Phrase searching

 

terms in phrase[tw] OR "terms in phrase"[tw]

NB: Do NOT use quotations around truncated phrases in PubMed as PubMed will then ignore the truncation symbol; PubMed will phrase search by default when the search field is specified after the phrase (except [all fields])


participatory research[tw]

terms in phrase.mp. OR "terms in phrase".mp.


participatory research.mp.

"terms in phrase"
TS=("participatory

research")

Truncation

 

terms in phrase*[tw]


rheumatoid nodule*[tw]

terms in phrase*.mp. OR terms in phrase$.mp.


rheumatoid nodule*.mp.

"terms in phrase*"
TS=("rheumatoid

nodule*")

Adjacency searching

(to search for a term within x terms from another term)

NA; AND terms together instead (or phrase search)


(patient[tw] AND outcome*[tw])

termA adjn termB


patient adj2 outcome*.mp.

NEAR/x (by default,

NEAR = NEAR/15)
TS=(brown NEAR "spider bite")

All databases - Boolean operators

Boolean operators

AND

  • retrieves records that include all of your search terms
  • e.g., diet therapy AND bulimia

OR

  • retrieves records that contain at least one of your search terms
  • e.g., (dog OR canine)

NOT

  • retrieves records that contain your first term but exclude your second term
  • e.g., dementia NOT alzheimer's
  • we do not usually recommend that you use NOT in your searches, as you may exclude relevant results

Note: Capitalize your operators as a matter of practice. In some databases, it does not matter whether you enter them in uppercase or lowercase, but others (like PubMed or Google Scholar) require them to be in uppercase.

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