UPDATED: November 17, 2025. Original Post: July 20, 2020
Integrating the best available health evidence into decision-making processes is an important part of evidence-based practice. However, before applying clinical research findings to patient care, health care providers must determine whether the research findings are valid.
It is important to remember that published studies are not necessarily trustworthy. Healthcare research must be evaluated before being used to guide clinical decisions. Critical appraisal provides a framework for this evaluation.
What is critical appraisal?
Critical appraisal is “the process of carefully and systematically examining research to judge its trustworthiness, and its value and relevance in a particular context.” (CASP)
To critically appraise clinical research is to look at its methodological quality, trustworthiness, and applicability to a patient’s specific situation. Critical appraisal helps us ask two essential questions about a particular research study (Sala Serra & Domingo Torrell, 2022):
- Are the results believable and free of bias or errors? (internal validity)
- Do the results apply to populations other than the sample participants, specifically to my patient’s situation? (external validity)
When should critical appraisal be conducted?
Research should always be critically appraised, no matter its intended use. Such uses may include:
- Patient care in a clinical setting
- Organizational policies or guidelines
- Care directives
- Educational projects
For example, if a recently published study in your discipline suggests a therapy is effective and safe for patients, critically appraising the study ensures the findings are valid and unbiased, and the therapy is appropriate for the specific needs of your patient.
Beyond clinical scenarios, critical appraisal is also a key part of evidence synthesis. As part of the systematic review process, for example, articles included in the review are critically appraised for validity. This ensures that the integrity of the overall review is not impacted by the quality of the individual studies included.
Using critical appraisal checklists
Any type of clinical study can be critically appraised, and each study type has its own checklist. Critical appraisal checklists provide a step-by-step guide through the appraisal process. There are many critical appraisal tools available from organizations that are experts in evidence-based research evaluation, including:
- JBI (formerly Joanna Briggs Institute): Critical Appraisal Tools
- Centre for Evidence-Based Medicine (CEBM): Critical Appraisal Tools
- Critical Appraisal Skills Programme (CASP): Critical Appraisal Checklists
- Scottish Intercollegiate Guidelines Network (SIGN): Critical Appraisal Notes and Checklists
- Critically Appraising for Antiracism Tool (Naicker, R. 2023)
For example, CASP’s Randomised Controlled Trial Checklist includes questions about study methodology such as:
- Was the assignment of participants to interventions randomised?
- Were the investigators ‘blind’ to the intervention they were giving to participants?
- Do the benefits of the experimental intervention outweigh the harms and costs?
- Would the experimental intervention provide greater value to the people in your care than any of the existing interventions?
Critical appraisal for antiracism is rarely addressed in standard tools. To avoid overlooking underrepresented patient populations, consider supplementing your chosen tool with Naicker’s Critically Appraising for Antiracism Tool.
Critical appraisal can be conducted without the use of a formal checklist, but using an established set of appraisal criteria may be helpful if you want to ensure that you are consistent in how you appraise clinical research.
For more info on critical appraisal in your daily work or a larger project, email AskLibrary@nshealth.ca or book a one-on-one consultation with a librarian.
Additional Support
In-depth Resources in Library Services' Searching subject guide.
References
1. CASP - Critical Appraisal Skills Programme. (2025, October 15). What is critical appraisal?. https://casp-uk.net/what-is-critical-appraisal/
2. Naicker, R. (2022). Critically appraising for antiracism. Education for Information, 38(4), 291–308. https://doi.org/10.3233/EFI-220052
3. Sala Serra, M., & Domingo Torrell, L. (2022). Validity of a study: Internal and external validity. Cirugia espanola, 100(10), 649–651. https://doi.org/10.1016/j.cireng.2021.12.007
Selena MacDonald
Librarian Educator
Nova Scotia Hospital, Central Zone
in the upper right corner of your screen, select Services and then Purchasing.
in the top right.
at the top of the full text.
let you navigate between all the results from the search results page.
(6). Click on each treatment option for further details (7).
What are Search Filters?
Search filters (also known as search hedges or search blocks) are pre-formulated search queries that are tailored to capture a concept as comprehensively as possible. They can be convenient and useful if you need help with devising a search strategy or if you search a concept often and would rather not input the same query every time.
For example, if you wish to create a search that explores the Canadian contexts of a given topic, then you may want to include a search query that completely captures the concept of ‘Canada’. The University of Alberta has some pre-fabricated search filters that could be useful. The one called ‘Canada and Provinces’, for example, contains different versions of the search filter for commonly used databases, such as Embase and CINAHL. The filters include subject headings and all grammatical variations of words used to describe Canada, the provinces, and the territories. In the search filter below, Canad* covers Canada, Canadian, and Canadians).
[mh Canada] or Canad* or "British Columbia" or "Colombie Britannique" or Alberta* or Saskatchewan or Manitoba* or Ontario or Quebec or "Nouveau Brunswick" or "New Brunswick" or "Nova Scotia" or "Nouvelle Ecosse" or "Prince Edward Island" or Newfoundland or Labrador or Nunavut or NWT or "Northwest Territories" or Yukon or Nunavik or Inuvialuit
From filters to retrieve studies related to Canada in CINAHL - University of Alberta
How do they work?
Search filters are very easy to use. First, find a search filter. You can either use a search engine and look up your concept with ‘search filter’ added to the search query, or you can try to find a search filter from an organization or group dedicated to developing and maintaining search filters. Two such groups are:
Once you find a search filter for your concept, ensure that it is designed for the database(s) you want to search. Then, simply copy and paste the search filter into the search box of the database. From there, you can combine that search filter with your other search concepts to develop your final search for your given research question.
How are they built?
Technically speaking, anyone can create a search filter. If you have a concept that you search often and find yourself entering the same query over and over, you could save that query as a text document for later use. That would count as a personal search filter.
Of course, not all search filters are created equal. Methods for devising them have changed and become more sophisticated with time. Initially, search filters were developed by librarians who had expertise in a given subject area. Some later search filters were validated with a gold standard or reference set of articles (i.e. if a search filter was able to pull all the articles within a reference set, then the search filter was likely specific enough for the concept). More recently, statistical and automated methods were developed to validate search filters. Although many methods of validation are now available, not all search filters are validated.
Frazier et al. (2015) explain the reference set validation method in detail. Their goal was to develop a validated search filter for ‘biomarkers for oral squamous cell carcinoma (OSCC)’. The method used in that paper started with developing a search strategy for general prognostic studies on OSCC. They reasoned that all studies on biomarkers for OSCC should be contained within that broader set. Then, at least two researchers independently screened the set of articles based on inclusion and exclusion criteria to produce the final set of articles on biomarkers for OSCC. (This is a high-level overview of their methods; please read the article for greater detail.)
How reliable are they?
Some search filters can be considered high quality if they have been validated. However, most search filters available are unvalidated, including those available from University of Alberta. This doesn’t mean they aren’t useful, but there is no guarantee that they will capture every article on a given topic. They can still be helpful when you only need to find a couple of key articles for a policy, a research assignment, or for patient care.
If you are working on a knowledge synthesis project (e.g. a scoping or systematic review) where comprehensiveness matters, it is best to use a validated search filter. Most validated search filters are published as journal articles and can be found by searching on databases or on websites that compile them (see ‘How do they Work?’, above). Kavanagh et al. (2021) present an example of a validated search filter. The tested search filters and their validity can be found in Table 1 of their article. They also outline exactly how the search filters were tested and validated.
The creation and validation of search filters is a whole field of study, but for most researchers and clinicians the most important thing to understand is where to find them and how to use them. For those working on knowledge synthesis projects, guideline development, or other cases where comprehensiveness is key, high quality validated search filters will be indispensable and convenient. For most other everyday uses, it is not necessary to use the most validated search filter, but rather the search filters that give you relevant results.
If you have questions about finding and using search filters or would like support in searching library resources, email AskLibrary@nshealth.ca or book a one-on-one consultation with a librarian.
Additional Support
Search Filters in Library Services' Searching subject guide.
References
1. Frazier, J. J., Stein, C. D., Tseytlin, E., & Bekhuis, T. (2015). Building a gold standard to construct search filters: A case study with biomarkers for oral cancer. Journal of the Medical Library Association, 103(1), 22–30. https://doi.org/10.3163/1536-5050.103.1.005.
2. Kavanagh, P. L., Frater, F., Navarro, T., LaVita, P., Parrish, R., & Iorio, A. (2021). Optimizing a literature surveillance strategy to retrieve sound overall prognosis and risk assessment model papers. Journal of the American Medical Informatics Association, 28(4), 766–771. https://doi.org/10.1093/jamia/ocaa232.
Vinson Li
Librarian Educator
Yarmouth Regional Hospital, Western Zone