"Evidence-Based Medicine is the integration of best research evidence with clinical expertise and patient values."
(Sackett DL, Straus SE, Richardson WS, et al. Evidence-based medicine: how to practice and teach EBM. 2nd ed. Edinburgh: Churchill Livingstone, 2000.)
When conducting EBP research on your topic or clinical question, it is important to consider the study methodology and corresponding quality of evidence that you find. The pyramid below reflects the hierarchy of evidence in the medical and scientific literature. Scroll down the page to see which resources you can use to find the various types of studies and review articles listed in the pyramid.
By CFCF - Own work, CC BY-SA 4.0, https://commons.wikimedia.org/w/index.php?curid=42857736.
TRIP (Turning Research Into Practice) Database Plus
Simultaneously searches evidence-based sources of systematic reviews, practice guidelines, and critically-appraised topics and articles -- including most of those listed above and many more. Also searches MEDLINE's Clinical Queries, medical image databases, e-textbooks, and patient information leaflets.
Filtered resources appraise quality of studies and often make recommendations for practice.
Systematic Reviews / Meta-Analyses
Authors of a systematic review ask a specific clinical question, perform a comprehensive literature search, eliminate the poorly done studies and attempt to make practice recommendations based on the well-done studies. A meta-analysis is a systematic review that combines all the results of all the studies into a single statistical analysis of results.
The Cochrane Database of Systematic Reviews
Consists of detailed, structured topic reviews of hundreds of articles. Teams of experts complete comprehensive literature reviews, evaluate the literature, and present summaries of the findings of the best studies. Published by the International Cochrane Collaboration.
The Database of Abstracts of Reviews of Effect (DARE)
Full-text database containing structured abstracts of systematic reviews from a variety of medical journals. DARE is produced by the National Health Services' Centre for Reviews and Dissemination (NHS CRD) at the University of York. DARE records cover topics such as diagnosis, prevention, rehabilitation, screening, and treatment.
Systematic Reviews are also searchable in MEDLINE:
- Ovid MEDLINE: Enter your search query > click the Additional Limits icon > select Systematic Reviews.
- PubMed MEDLINE: Enter a search query > go to Article Types in the left-hand menu > select More... > select Systematic Reviews so that this option appears in the menu > select Systematic Reviews to filter your results. Or, from the main PubMed search screen, select "Clinical Queries" in the middle column > enter a search query > artices that are considered Systematic Reviews are listed in the center of the results page.
Guidelines and Critically-Appraised Topics
Authors of guidelines and critically-appraised topics evaluate and synthesize multiple research studies.
Evidence-based clinical practice guidelines and related summaries produced by the National Guideline Clearinghouse/Agency for Health Care Research and Quality.
Note: Guideline evidence varies from expert opinion to high levels of evidence.
United States Preventive Services Task Force recommendations for primary care practice.
The ACP Journal Club / EBM Reviews
The editors of this journal screen the top 100+ clinical journals and identify studies that are methodologically sound and clinically relevant. An enhanced abstract, with conclusions clearly stated, and a commentary are provided for each selected article. Published by the American College of Physicians-American Society of Internal Medicine.
Evidence is not always available via filtered resources. Searching the primary literature may be required. It is possible to use specific search strategies in MEDLINE and other databases to achieve the highest possible level of evidence.
To limit your PubMed search to the best evidence-producing studies, click on "Clinical Queries" under PubMed Tools (in the middle column of the screen). This specialized search is intended for clinicians and has built-in search filters. Five study categories--therapy, diagnosis, etiology, prognosis, clinical prediction guides--are provided. You can also limit your search to various study types (systematic reviews, cohort, randomized controlled trials, etc.). From the PubMed search screen, enter a search query > go to Article Types in the left-hand menu > select More... > select the types of studies that wish to appear appear as optional filters on your results page.
To limit your Ovid MEDLINE search to the best evidence-producing studies, enter your search query > click the Additional Limits icon > select Evidence Based Medicine Reviews or Systematic Reviews.
Cumulative Index to Nursing and Allied Health Literature
Limit your CINAHL search to the best evidence-producing studies by choosing various filters in the Search Options section of the page (e.g. select Evidence Based Practice, or choose a specific type of study from the Clinical Queries or Publication Type menus).
A large abstract and citation database that includes biomedical literature (100% of the MEDLINE records), as well as journals in the life and social sciences. Limit your search to Articles under the Document Type filter.
Note: Evidence in these resources may vary from expert opinion to high levels of supported evidence.
A clinical information resource, which offers up-to-date, fully referenced expert answers to patient-care, diagnosis, and treatment questions. Topic reviews are written by recognized authorities who review the topic, synthesize the evidence, summarize key findings, and provide specific recommendations.
Physician authors and editors contribute to this free clinical knowledge base, which contains articles on 7,000 diseases and disorders. The evidence-based content undergoes multiple levels of physician peer review and provides the latest practice guidelines in 62 medical specialties.
Full-text electronic books through STAT!Ref and TDS Health.
|Levels of evidence|
|1||One or more randomized controlled clinical trials of sufficient sample size with a narrow confidence intervalMeta-analysis of randomized controlled clinical trials|
|2||Good quality cohort studyLow-quality randomized clinical trial (small sample size and >20% lost to follow-up)|
|3||Case-control studiesMeta-analysis of case-control studies|
|4||Case seriesLow-quality cohort studiesLow-quality case-control studies|
|5||Based on expert opinions, experimental studies or physiology|
|Grade/Strength of recommendation|
|A||Corresponding to level of evidence 1|
|B||Corresponding to level of evidence 2 or 3Extrapolated from level 1 studies involving populations other than the current population|
|C||Corresponding to level of evidence 4Extrapolated from level 2 or 3 studies involving populations other than the current population|
|D||Corresponding to level of evidence 5|
Adapted from: Levels of evidence and grades of recommendation, Oxford Center for Evidence-Based Medicine, May 2001.
Table 5 in Giavina-Bianchi P, et al. Clinics, 2011; 66(9):1627-36. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3164416/. Open Access content distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/3.0/).
Use these forms to better define your own research question and search strategy.
The Centre for Evidence-Based Medicine (Oxford) provides several resources that take you through the entire EBM process, from formulating questions to evaluating the literature to making informed clinical decisions.
Contact a librarian if you would like some help searching for information on your topic or tracking down the full text of an article. That's why we're here!