Types of evidence

Various systems have been developed to rank evidence. Here are two examples.

 

The Canadian Institutes for Health Research (2009) created a hierarchy of quantitative evidence:

• systematic reviews of randomized controlled trials;
• randomized controlled trials;
• systematic reviews of nonrandomized or cohort studies;
• cohort studies;
• case control studies;
• case series;
• case report;
• ideas, editorials, opinions;
• animal research; and
• invitro (test tube) research.

Brian Haynes (2007) developed the 5S Pyramid for finding the best evidence with the least amount of time and effort:

Studies are individual studies related to a particular focused question. There are several searchable databases that would help you find individual studies. The most used in Canada include Medline, PubMed and CINAHL, but there are many other specialized databases.

 

Syntheses include systematic reviews of all studies that could be found on a particular focused question. These include The Cochrane Library, Worldviews on Evidence-Based Nursing, the Agency for HealthCare Research and Quality (AHRQ) Evidence-based Practice Centre Reviews. Both groups have similar, rigorous methods for review. Another source for systematic reviews and summaries about interventions related to public health in Canada is the Effective Public Health Practice Project. Further, Health-Evidence.ca rates reviews that are relevant to public health in Canada, summarizes them and provides recommendations for practice and policy that arise from the reviews.

 

Synopses are brief reports (1-2 pages) of pre-appraised individual studies or systematic reviews that give key methodological details and results, along with an expert commentary, on issues of applying the results in practice. Examples of synopses are found in 23 evidence-based journals that cover topics such as medicine, nursing, dentistry and health policy (e.g., Evidence-Based Nursing ).

 

Summaries are usually text-based and are related to a specific disease or condition (e.g., Clinical Evidence).

 

Systems are electronic systems that can be linked to patient records and prompt practitioners with guidelines for care (e.g., what tests to order, what interventions to provide). For example, for a patient with type 2 diabetes, it would prompt the caregiver that blood work, eye exam, foot exam and diet review need to be done.