Critical appraisal is the process in which we determine the reliability, value, and relevance of research before applying it to clinical decisions. Critical appraisal can help combat information overload, identify the most clinically relevant articles, and aid in continuing professional development. Below you can find some common questions that you can ask about a study to help critically appraise it.
Common Questions:
Not all study types are equal in regards to the quality of evidence and potential of bias to creep into the study. The pyramid below demonstrates the quality of evidence hierarchy between different study types.
The highest quality studies: Meta-Analyses/Systematic Reviews at the top and expert opinions, and individual case reports near the bottom.
The risk of bias in study types is generally higher towards the bottom and lessens towards the top of the pyramid. However, keep in mind the concept of "garbage in - garbage out." If a systematic review from the top of the pyramid collects and summarizes only low quality observational studies from the bottom of the pyramid, it is not actually much stronger than those original lower quality studies.
For a description of the different types of studies consult the glossary descriptions below.
Individual Case Report
A detailed report of the diagnosis, treatment, and follow-up of an individual patient. Case reports also contain some demographic information about the patient (for example, age, gender, ethnic origin).
Case-Control Study
A study which involves identifying patients who have the outcome of interest (cases) and patients without the same outcome (controls), and looking back to see if they had the exposure of interest.
Case Series
A report on a series of patients with an outcome of interest. No control group is involved.
Clinical Practice Guideline
A systematically developed statement designed to assist clinician and patient decisions about appropriate health care for specific clinical circumstances.
Cohort Study
Involves identification of two groups (cohorts) of patients, one which received the exposure of interest, and one which did not, and following these cohorts forward for the outcome of interest.
Meta-Analysis
A systematic review that uses quantitative methods to synthesize and summarize the results.
Non-Randomized Controlled Trial
A clinical trial in which the participants are not assigned by chance to different treatment groups. Participants may choose which group they want to be in, or they may be assigned to the groups by the researchers.
Randomized Controlled Trial
Participants are randomly allocated into an experimental group or a control group and followed over time for the variables/outcomes of interest.
Systematic Review
A summary of the medical literature that uses explicit methods to perform a comprehensive literature search and critical appraisal of individual studies and that uses appropriate statistical techniques to combine these valid studies.
Definitions from 1) Glossary of EBM Terms.https://ebm-tools.knowledgetranslation.net/resource/glossary and 2) National Cancer Institute Dictionary. https://www.cancer.gov/publications/dictionaries/cancer-terms Retrieved Oct. 2019
