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 is important to find out if there are other knowledge syntheses that have been published or that are in the process of being published on your topic.
If you are submitting your review or study for funding, for example, you may want to make a good case that your review or study 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.
In the context of conducting a review, even if you do find one on your topic, it may be sufficiently out of date or you may find other defendable reasons to undertake a new or updated one. In addition, looking at other knowledge syntheses published around your topic may help you refocus your question or redirect your research toward other gaps in the literature.
The Cochrane Library (including systematic reviews of interventions, diagnostic studies, prognostic studies, and more) is an excellent place to start, even if Cochrane reviews are also indexed in MEDLINE/PubMed.
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. 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.
To limit your search strategy to systematic reviews: Go to Additional Limits, and under EBM-Evidence Based Medicine, choose Systematic Review.
Alternatively, you can use a search hedge/filter; for example, the filter used by BMJ Best Practice to find systematic reviews in Embase (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 or RETRACTED ARTICLE/) or (systematic$ adj2 (review$ or overview)).ti,ab.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.
Alternative interface to PubMed: You can also search MEDLINE on the Ovid platform, which we recommend for systematic searching. Perform a sufficiently developed search strategy (be as broad in your search as is reasonably possible) and then, from Additional Limits, select the publication type Systematic Reviews, or select the subject subset Systematic Reviews Pre 2019 for more sensitive/less precise results.
The subject subset for Systematic Reviews is based on the filter version used in PubMed.
Perform a sufficiently developed search strategy (be as broad in your search as is reasonably possible) and then, from Additional Limits, select, under Methodology, 0830 Systematic Review
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 published by collaborations like Cochrane, Campbell, BEME or JBI, for example, may require more careful critical appraisal for quality.
See Systematic Reviews Search Strategy Applied in PubMed for details.