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EPIB-619: Systematic Reviews & Meta-Analyses

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Has your review or synthesis already been done?

Has your review or synthesis already been done?

Finding systematic reviews or syntheses on your topic

Once you have a reasonably well defined research question, it is important to make sure your project has not already been recently and successfully undertaken. This means it’s important to find out if there are other research syntheses (including systematic reviews) that have been published or that are in the process of being published on your topic.

If you are submitting your systematic review for funding, for example, you may want to make a good case that your review or synthesis is needed and not duplicating work that has already been successfully and recently completed—or that is in the process of being completed. It is also important to note that what is considered “recent” will depend on your discipline and the topic.

Even if you do find another review or synthesis on your topic, it may be sufficiently out of date or you may find other defendable reasons to perform it again. In addition, looking at other research syntheses published around your topic may also help you refocus your question or redirect your research toward other gaps in the literature.

These tips may not cover every possible type of research synthesis but they provide a decent start.

To find other reviews or syntheses:

To find other reviews or syntheses:

Search databases specifically focused on systematic reviews using a very broad search strategy, databases such as:

The Cochrane Library (including systematic reviews of interventions, diagnostic studies, prognostic studies, and more) is an excellent place to start.

By default, the Cochrane Library will display “Cochrane Reviews” (Cochrane Database of Systematic Reviews, aka CDSR). You can ignore the results which show up in the Trials tab when looking for systematic reviews: They are records of controlled trials relevant to Cochrane reviews. There is also an option to see Other Reviews under "More".

The example shows the number of Cochrane Reviews with hiv AND circumcision in the title, abstract, or keywords.

In addition, you can perform a sufficiently developed search strategy on MEDLINE via PubMed (be as broad in your search as is reasonable) and then use the “Article types” filter for “Systematic Reviews” to see if other reviews have been published on your topic. Systematic reviews found in PubMed and not included in The Cochrane Library may require more careful critical appraisal for quality assessment.

See Systematic Reviews Search Strategy Applied in PubMed for details.


Alternative interface to PubMed: You can also search MEDLINE on the Ovid platform. Perform a sufficiently developed search strategy (be as broad in your search as is reasonable possible) and then apply the "limit" under Publication Types for Systematic Reviews (it is, in fact, a search filter, and not a publication checktag/limit; because it is not a checktag/limit, it is not as accurate).

The Systematic Reviews search strategy is based on the version used in PubMed.

From additional limits, under EBM-Evidence Based Medicine, choose Systematic ReviewOnce you have run your search, to limit to systematic reviews: Go to Additional Limits, and under EBM-Evidence Based Medicine, choose Systematic Review

Other approaches: To search for systematic reviews in Embase on Ovid, perform a reasonably developed search strategy (be as broad in your search as is reasonably possible) and then combine your search results with a systematic review filter developed for Embase on Ovid, e.g., filters available at

Example of a filter used to find systematic reviews for BMJ Clinical Evidence (can be copied and pasted into the Embase search box then combined with the concepts of your research question):

(exp review/ or (literature adj3 review$).ti,ab. or exp meta analysis/ or exp "Systematic Review"/) and ((medline or medlars or embase or pubmed or cinahl or amed or psychlit or psyclit or psychinfo or psycinfo or scisearch or cochrane).ti,ab. or RETRACTED ARTICLE/) or (systematic$ adj2 (review$ or overview)).ti,ab. or (meta?anal$ or meta anal$ or meta-anal$ or metaanal$ or metanal$).ti,ab.

Additional, specialized databases you can search to find existing or in-process reviews

Database and platform cheat sheet

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




Ovid Online


Web of Science
Command Search

Subject headings


MeSH (Medical Subject Headings)


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

exp subject heading/

"Explode" to include narrower terms
exp tuberculosis/



Searching major subject headings

"MeSH term"[majr]

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


exp *subject heading/

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

exp *tuberculosis/


Searching title/abstract




Searches author keywords too



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




Searching title terms








Searching title/abstract/
entry terms





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 OR "terms in phrase".mp.


"terms in phrase"




terms in phrase*[tw]

rheumatoid nodule*[tw]

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

rheumatoid nodule*.mp.

"terms in phrase*"


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,

TS=(brown NEAR "spider bite")

RCT search filters for MEDLINE on Ovid, EMBASE on Ovid, and PubMed

Use these pre-formulated search strategies (database-specific) to increase the sensitivity of a search for randomized controlled trials. to do so, just copy and paste the appropriate strategy into the database search box:

RCT search filters/hedges

PubMed highly sensitive filter/hedge for RCTs, modified with addition of randomised[tiab]:

((randomized controlled trial[pt]) OR (controlled clinical trial[pt]) OR (randomized[tiab] OR randomised[tiab]) OR (placebo[tiab]) OR (drug therapy[sh]) OR (randomly[tiab]) OR (trial[tiab]) OR (groups[tiab])) NOT (animals[mh] NOT humans[mh])


Box 6.4.a,


MEDLINE on Ovid highly sensitive filter/hedge for RCTs, modified with addition of randomised.ab.

((randomized controlled trial or controlled clinical trial).pt. or randomized.ab. or randomised.ab. or placebo.ab. or drug therapy.fs. or randomly.ab. or trial.ab. or groups.ab.) not (exp animals/ not


Box 6.4.c,


Embase on Ovid filter/hedge for controlled trials:

crossover-procedure/ or double-blind procedure/ or randomized controlled trial/ or single-blind procedure/ or (random* or factorial* or crossover* or cross over* or placebo* or (doubl* adj blind*) or (singl* adj blind*) or assign* or allocat* or volunteer*).tw.

Source: What is in The Cochrane Central Register of Controlled Trials (CENTRAL) from EMBASE?

(NB: does not remove animal studies as the MEDLINE version does)

Other filters/hedges

Other filters/hedges

The Systematic Reviews wiki includes a list of other sites containing filters/hedges (both validated and unvalidated) as well as some specific ones for indigenous health in Canada, Canada and Low and Middle Income Countries (2012).

Exporting search results to EndNote

Exporting search results into EndNote

Note: This procedure helps you keep track of the information that will be needed to report the methods in the article and also to fill in the PRISMA flow diagram.

Have the right EndNote library open in the background before you begin exporting.

Note: We do not generally recommend using Safari as your browser during this process, although it can be used with some tweaking.

For more instructions on using EndNote or other software programs, please see the Citation Guide

The steps below cover Ovid MEDLINE, Embase Classic+Embase on Ovid, PubMed, and Web of Science.

Exporting from Ovid Online

Exporting from Ovid Online

(MEDLINE, Embase, PsycINFO, Global Health)

We often start by exporting records from Ovid MEDLINE, if applicable (you may have decided to only use PubMed to search MEDLINE; those instructions are below):

  1. In EndNote, create a new library, with a useful name like SearchConcepts-MEDLINE-yyyymmdd-xRecords.enl, for the records from the database in question (e.g., MEDLINE on Ovid) and have the library ready in the background
  2. From Ovid, export complete reference in groups of <= 1000 (e.g., 1-1000, 1001-2000), do this until all of your records are exported (Export > Export To: EndNote; Select Fields to Display: Complete Reference; Export Citations)

  1. Move batches of exported records to the library you created and check the final number of records in the library against the number of results listed in database
  2. From Ovid MEDLINE: Download the search history for your records: Export (1, 1-10) > choose Microsoft Word format, check off Search History, and save the Word document to your documentation folder, with a useful filename in a format like SearchConcepts-yyyymmdd-Search-MEDLINE-xRecords, SearchConcepts-yyyymmdd-Search-Embase-xRecords...
    • Not including the records themselves, the search history can then be copied and pasted into an appendix of the article, to document the search strategy with exactness. Avoids transcription errors
  3. Save the search history to your personal Ovid account (free) and identify the search by database name and date; this greatly facilitates rerunning the search later if an update is needed
  4. Create a compressed version of the EndNote library for your records

Exporting from PubMed

Exporting from PubMed

  1. In EndNote, create a new library, with a useful name like SearchConcepts-PubMed-yyyymmdd-xRecords.enl, for the records from the database in question (PubMed) and have the library ready in the background
  2. From PubMed, Click on Send To > Choose Destination: File > Format: MEDLINE > Create File

  1. In Firefox: Open with EndNote

  1. If the file was saved to your computer instead of automatically being imported into EndNote, import the file into EndNote (In EndNote menu: File > Import > File and locate the saved PubMed file on your computer) > Select PubMed (NLM) filter (if not visible, click “Other Filters…” to find it)


  1. Save the search history for your records: From PubMed: Click Create alert under the search box or from the Advanced screen, click Download history to maintain the line-by-line version (if applicable). The search is saved in an agglomerated format but this is useful if you need to rerun the search later for an update
  2. Create a compressed version of the EndNote library for your records

Creating a backup, compressed EndNote library for your records

Create a backup, compressed EndNote library for your records

  • Before merging the libraries, create compressed libraries of each of the EndNote libraries from the individual database searches: Keep these compressed libraries for your records (you can also back these up as, e.g., RIS files, to save space)
  • Using the uncompressed versions of those libraries, bring all the records from your separate searches in to one EndNote library if you haven’t done so already: From EndNote menu, File > Import > File > locate individual .enl files; Import: EndNote library. You will perform deduplication in this library.

Creating a new EndNote library for deduplication and backup after deduplicating

Create a new EndNote library for deduplication and backup after deduplicating

Removing duplicates

See the instructions on deduplicating in EndNote.

Create a compressed library for backup after having removed all duplicates, with a filename like SearchTerms-yyyymmdd-Deduplicated—xRecords.enlx. This will be the library for screening.

Important information to document

Important information to document for the search

Record the information in a separate document:

Information Example
Names of databases/platforms searched Ovid MEDLINE
Database time coverage 1946-Present
Date searched January 12, 2018
Number of records from each database before deduplicating

Ovid MEDLINE: 1023

Ovid Embase: 2046

Number of records after deduplicating 2056
Search strategy from each database


1. Silicone gels/
2. Silicone elastomers/
3. Silicon*.tw.
4. (gels or gel).tw.
5. Cica
6. Or/1–5
7. Cicatrix, hypertrophic/
8. (hypertrophic adj3 scar*).tw.
9. Hypertrophic
10. Hypertrophic
11. Or/7–10
12. 6 and 11



Genevieve Gore's picture
Genevieve Gore
Schulich Library of Science & Engineering
Website Skype Contact: genatlibrary

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