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Search filters and hedges overview
Search hedges are pre-made search strategies which can be incorporated into your search, saving you time.
may be methodological or topic-based.
can also be referred to as clinical queries, optimal search strategies or filters.
(however these are NOT the same as the filters you will see in databases) may be formally 'validated' to meet a minimum level of article retrieval sensitivity and precision.
Watch this video from Yale University for an introduction to pre-made search strategies and suggestions of where to find validated hedges.
Video Length: 10:57
Building systematic search strategies is complex and time consuming.
It can be worth searching for pre-made search strategies that match your concepts.
Pre-made search strategies are known as 'filters' or 'hedges'.
They may also be called 'optimal search strategies', 'quality filters', or 'clinical queries'.
Topic hedges are designed to find resources relevant to a specific topic.
Methodological hedges are designed to find specific study design types.
These can save time, but there are things to consider before deciding to use existing hedges.
Some hedges are expert informed, using scientific validation techniques.
Validated sets have been examined to determine their sensitivity and specificity.
If a hedge has a sensitivity of 99%, it will retrieve 99% of all articles known to be
relevant in a gold standard test set. A hedge with high sensitivity will be very comprehensive, but will require you to filter out some irrelevant results.
If a hedge has a specificity of 99%, it filters out 99% of articles that are known to be
irrelevant in the gold standard test set. A hedge with high specificity will be extremely focused, but may miss some relevant results.
In most cases, you will end up choosing a hedge that has a balance of sensitivity and specificity.
Not all hedges are validated - this doesn't mean they are poor quality, but you will have to carefully evaluate the hedge yourself.
If a hedge has been validated, consider:
the sensitivity and specificity score
the database used for validation
if you will need to remap the hedge to a new database
the subject area of the gold standard test set
the date of the validation
For details about where to search for hedges, please continue reading the information on this page.
How do I choose one?
Consider whether the search hedge is:
current? Subject headings do change over time.
relevant to your PICO / PICO element?
comprehensive and transparent?
validated? What methods were used to develop it?
created by an expert Information Manager / Librarian or research group?
cited? (Search hedges should be cited when used. If a hedge has
not been cited many times, this may indicate insufficient quality.)
Use a checklist or ranking tool:
Note: If you edit or update a validated hedge, or apply it outside its tested database or subject area, it is no longer considered validated – so you cannot guarantee the level of sensitivity and/or precision.
Guidelines and standards
'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
Sources of hedges / filters
ISSG search filters resource
Hedges include: adverse effects, aetiology, diagnostic studies, economic evaluations, epidemiological studies, guidelines, health services research, health state utility values, mixed methods studies, non-randomised studies, observational studies
SIGN (Scottish Intercollegiate Guidelines Network) search filters
Hedges include: systematic reviews, randomised controlled trials, observational studies, diagnostic studies, economic studies, patient issues
Center for Evidence-Based Management (CEBMa)
Hedges include: meta-analysis/systematic reviews, controlled/longitudinal studies
Cochrane Manual: Search Filters
Cochrane manual statement on filters (Chapter 4: Searching for and selecting studies).
Cochrane Technical Supplement: Search Filters
Includes filters to identify randomised controlled trials in a number of databases.
Hedges include: therapy, diagnosis, review, prognosis, causation (etiology), economics, cost, clinical prediction guides, qualitative
Hedges include: systematic reviews/meta-analysis/health technology assessment, randomised controlled trials, guidelines, economic evaluations/cost/economic models, health utilities/quality of life, narrow economic filter
Flinders Filters (including CareSearch Filters)
Includes: Integrated care; Bereavement, Grief and Loss; Contraception; Dementia; Opthalmology; Heart Failure; Aboriginal and Torres Strait Islander Health; Lung Cancer; Palliative Care; Primary Health Care; Residential Aged Care; Stroke
Ovid Expert Searches
A range of search hedges on current health topics, diseases and treatments for use in Medline and Embase. Most are not validated.
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