Formulating a well-constructed research question is essential for a successful review. You should have a draft research question before you choose the type of knowledge synthesis that you will conduct, as the type of answers you are looking for will help guide your choice of knowledge synthesis.
|A systematic review question||A scoping review question|
|Typically a focused research question with narrow parameters, and usually fits into the PICO question format||Often a broad question that looks at answering larger, more complex, exploratory research questions and often does not fit into the PICO question format|
|Example: "In people with multiple sclerosis, what is the extent to which a walking intervention, compared to no intervention, improves self-report fatigue?"||Example: "What rehabilitation interventions are used to reduce fatigue in adults with multiple sclerosis?"|
Developing a good research question is not a straightforward process and requires engaging with the literature as you refine and rework your idea.
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 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Even if you do find another review or synthesis on your topic, it may be sufficiently out of date or you may find other defendable reasons to perform it again.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 knowledge syntheses published around your topic may also 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.
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 reasonably 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, but conversely, it will include unindexed records if your search included textwords/keywords, which is an advantage).
The Systematic Reviews search strategy is based on the version used in PubMed.
Once you have run your search, to limit 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 Clinical Evidence 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.