There are different study types used for the evidence base in systematic reviews. Below are some definitions of the different study types that may be used.
- Randomized controlled trials (RCT)
A group of patients is randomized into an experimental group and a control group to test the efficacy of a treatment/intervention.
- Cohort study
Involves the identification of two groups (cohorts) of patients, one which did receive the exposure of interest, and one which did not, and following these cohorts forward for the outcome of interest.
- Case-control study
Involves identifying patients who have the outcome of interest (cases) and control patients without the same outcome, and looking to see if they had the exposure of interest. Just like cohort studies, case-control studies are observational.
-
Cross-sectional study
Typically involves the surveying of a randomly selected group to find out their opinions or facts. These studies can answer questions such as how common a particular disease is, but cause and treatment of the disease cannot be gleaned.
- Qualitative study
Collects information on patients with diseases and those close to them. Requires specialized tools for analyzation and interpretation. These studies typically want to access a person's experience.
-
Meta-analysis
A statistical analysis, which can either be a study in itself or a component of another study type. It uses quantitative methods to summarize the results of scientific studies.
For further reading
Check out the Institute for Quality and Efficiency in Health Care (IQWiG) article What types of studies are there? offered through the National Center for Biotechnology Information, U.S. National Library of Medicine.
