You may want to think about criteria that will be used to select articles for your literature review based on your research question. These are commonly known as inclusion criteria and exclusion criteria, and they set the boundaries for the literature review.
Inclusion and exclusion criteria are determined after formulating the research question but usually before the search is conducted (although preliminary scoping searches may need to be undertaken to determine appropriate criteria). It may be helpful to determine the inclusion criteria and exclusion criteria for each PICO component.
Be aware that you may introduce bias into the final review if these are not used thoughtfully.
Inclusion and exclusion are two sides of the same coin, so—depending on your perspective—a single database filter can be said to either include or exclude. For instance, if articles must be published within the last 3 years, that is inclusion. If articles cannot be more than 3 years old, that is exclusion.
The most straightforward way to include or exclude results is to use database limiters (filters), usually found on the left side of the search results page.
Inclusion criteria are the elements of an article that must be present in order for it to be eligible for inclusion in a literature review. Some examples are:
Exclusion criteria are the elements of an article that disqualify the study from inclusion in a literature review. Some examples are: