When answering clinical questions, you need to use the highest level of evidence possible. In the diagram below, evidence that is higher up the pyramid is of higher quality i.e., systematic reviews (secondary research).
A systematic review is regarded as a high level of evidence and is secondary research. It starts with a specific and answerable clinical question, identifies all the research available and eliminates flawed and low-quality studies, then uses the results of the remaining high-quality studies to answer the clinical question and thus make recommendations on best practices.
Randomised controlled trials are primary research. Researchers assign participants randomly into an intervention group or a control group, then results are compared to see if the intervention had an effect.
A cohort study is primary research. It looks at the health outcomes of a specified group, comparing people in the group who have been exposed to a potential risk factor with those who have not been exposed, and looks for links and correlations.
Case control studies looks at existing data to compare people who have a specific health outcome or condition, compared with those who don't, to find what factors differ between the groups.
Case series and case reports look at one or more individual cases and outcomes or responses to interventions. Regarded as a low level of evidence, the information might not apply to a wider population.
Editorials and expert opinions can be based on a practitioner's individual experience. Generally regarded as one of the lowest levels of acceptable evidence, they do not necessarily account for uncontrolled external factors, differences between different groups, nor placebo effects.
Hover over each level of the evidence pyramid for more detail
To learn more about levels of evidence, click on the links below:
Joanna Briggs Institute. (2013). JBI levels of evidence. JBI. https://jbi.global/sites/default/files/2019-05/JBI-Levels-of-evidence_2014_0.pdf
More explanation:
Joanna Briggs Institute Levels of Evidence and Grades of Recommendation Working Party. (2014). Supporting document for the Joanna Briggs Institute levels of evidence and grades of recommendation. JBI. https://jbi.global/sites/default/files/2019-05/JBI%20Levels%20of%20Evidence%20Supporting%20Documents-v2.pdf
Nice tabular summary of the JBI levels of evidence:
JBI, & University of Adelaide. (2021). JBI EBP database guide. Wolters Kluwer. https://ospguides.ovid.com/OSPguides/jbidb.htm
