Search filters and hedges 

You may want to apply certain criteria to your search results, eg study types, or population groups.

DO NOT USE THE IN-BUILT FILTERS IN DATABASES - they are unreliable.

However constructing your own search filter (AKA search hedge) is complex. Instead use pre-existing filters which you can add to your search strategy.

These have often been validated for accuracy. If you use a validated search filter you should report it in your methods.

Key points

• Pre-made search strategies that match your concepts can help your process
  • Pre-made search strategies are known as 'filters' or 'hedges'.
  • 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 filters have been expertly validated
• If a filter has been validated, consider its balance of sensitivity and specificity 
  • A filter with high sensitivity will be very comprehensive, but will require you to filter out more irrelevant results.
  • A filter with high specificity will be extremely focused, but may miss some relevant results.
  • In most cases, you will end up choosing a filter that has a balance of sensitivity and specificity.
• Not all filters are validated - this doesn't mean they are poor quality, but you will have to carefully evaluate the hedge yourself.
• You may choose to use only some elements of a pre-existing search filter
• Filters are validated to named databases
  • You may need to remap the hedge to other databases 

 Make an appointment with a librarian for help identifying relevant filters for your search. 

Sources of filters/hedges

Below are links to some commonly used filters you may find useful.

• The ISSG search filter resource (InterTASC Information Specialists' Sub-Group)

  '...lists known filters of interest to researchers producing technology assessments' - multiple categories, for example adverse effects; age groups; guidelines; qualitative research; systematic reviews; quality of life

• Cochrane Handbook, part 2, chapter 4, section 4.4.7: Search filters  Includes filters to identify randomised controlled trials in a number of databases
• Pubmed Clinical Queries  Enter your search term and your results will be automatically categorised into Clinical Study Categories, Systematic Reviews and Medical Genetics. 
• CINAHL Clinical Queries allow the user to limit searches using specific search strategies to aid in retrieving scientifically sound and clinically relevant study reports indexed in CINAHL databases.
• CADTH Database Search Filters

  A list of commonly used filters from the Canadian Agency for Drugs and Technologies in Health (CADTH).

• Search filters - SIGN (Scottish Intercollegiate Guidelines Network)

  Filters include: systematic reviews; randomised controlled trials; observational studies; diagnostic studies; economic studies; patient issues

• Strings Attached: CADTH's Database Search Filters

  Canadian Agency for Drugs and Technologies in Health. Filters 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 (Flinders University) (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

• Expert Searches - Ovid Tools & Resources Portal (Wolters Kluwer)

  A range of search filters for use in MEDLINE and Embase - primarily focused on current health topics, diseases, and treatments. Most are not validated

• Topic search filters: a systematic scoping review (R. Damarell et al.)

  This scoping review identifies 58 filters across a range of topics. Damarell, R. A., May, N., Hammond, S., Sladek, R. M., & Tieman, J. J. (2019). Health Information & Libraries Journal, 36(1), 4-40. https://doi.org/10.1111/hir.12244

• Hedges - Health Information Research Unit (HIRU), McMaster University

  Filters include: therapy, diagnosis, review, prognosis, causation (etiology), economics, cost, clinical prediction guides, qualitative

• Methodological Search Filters - CEBMa (Center for Evidence-Based Management)

  Filters include: meta-analyses and systematic reviews; controlled and/or longitudinal studies

• CareSearch Search filters for palliative care, heart failure, dementia, residential aged care and dementia.

• McMaster / Health Informatics Research Unit Hedges  Search filters or hedges to improve retrieval of scientifically sound and clinically relevant study reports from large, general-purpose, biomedical research bibliographic databases including MEDLINE, EMBASE, and PsycINFO.