Search filters (also known as 'hedges') are pre-made search strategies you can incorporate into your search, saving you time.
Filters:
This video from Yale University provides an introduction to pre-made search strategies and suggestions of where to find validated filters.
Video Length: 10:57
More information
Consider whether the search filter is:
'All search filters and all search strategies are compromises and an assessment of the performance of filters for your own research should always be made.' - 'What is the ISSG Search Filter Resource?', ISSG Search Filters Resource |
Use a checklist or ranking tool:
There are a couple of approaches to limiting to randomised controlled trials: search filters, and machine learning tools such as that available via Covidence.
Using search filters is only recommended for certain databases, and where numbers of results prohibit reasonable screening loads. It is not needed for Cochrane Library which is already limited to trials in humans.
The Cochrane search filters (provided for PubMed, MEDLINE via Ovid, Embase via Ovid and CINAHL via EBSCOhost) have the humans and RCTs filtering built in together; this can be separated out and only the appropriate section applied if needed for your review.
See the Sources of filters box on this page for other available filters for randomised controlled trials (e.g. CADTH, SIGN).
The Cochrane Randomized Controlled Trial (RCT) classifier is a machine learning tool integrated into Covidence that tags records as 'Possible RCT' or 'Not RCT'.
The following are possible approaches for limiting your results to human studies, without excluding those where both humans and animals are mentioned, and addressing limitations in 'Humans' database limits (typically a checkbox or menu option, where available).
For the purposes of demonstration line number 10 is taken as the final search line with all of your concept sets combined.
MEDLINE via Ovid
10 your final set of results before applying limits (e.g. topic sets 3 AND 9)
11 10 NOT (exp animals/ NOT humans.sh.)
Source: Cochrane Handbook for Systematic Reviews of Interventions, Technical Supplement to Chapter 4: Searching for and selecting studies, Section 3.6.1 The Cochrane Highly Sensitive Search Strategies for identifying randomized trials in MEDLINE
Embase via Ovid
10 your final set of results before applying limits (e.g. topic sets 3 AND 9)
11 (rat OR rats OR mouse OR mice OR swine OR porcine OR murine OR sheep OR lambs OR pigs OR piglets OR rabbit OR rabbits OR cat OR cats OR dog OR dogs OR cattle OR bovine OR monkey OR monkeys OR trout OR marmoset$1).ti. AND animal experiment/
12 Animal experiment/ NOT (human experiment/ OR human/)
13 11 OR 12
14 10 NOT 13
Source: Cochrane Handbook for Systematic Reviews of Interventions, Technical Supplement to Chapter 4: Searching for and selecting studies, Section 3.6.2 Search filters for identifying randomized trials in Embase
CINAHL via EBSCOhost
10 your final set of results before applying limits (e.g. topic sets 3 AND 9)
11 MH animals+
12 MH (animal studies)
13 TI (animal model*)
14 S11 OR S12 OR S13
15 MH (human)
16 S14 NOT S15
17 S10 NOT S16
Source: Cochrane Handbook for Systematic Reviews of Interventions, Technical Supplement to Chapter 4: Searching for and selecting studies, Section 3.6.3 Cochrane CINAHL Plus filter
While it is relatively common to have English language as an inclusion criterion, the best practice recommendation is to manage this in the screening rather than applying it during the search by limiting/refining the search to English language. The following support and expand on this:
Can't find a quality, recognised filter for your database and platform/interface?
In this case you can either:
The second option is most commonly adopted when the number of records is problematic for screening given your available resources.
'If published approaches such as search filters…or search strategies from other systematic reviews, were used, cite them. If published approaches were adapted…note the changes made.' - PRISMA 2020 Explanation and Elaboration, p. 7
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