Identify the criteria that will be used to determine which research studies will be included. The inclusion and exclusion criteria must be decided before you start the review. Inclusion criteria is everything a study must have to be included. Exclusion criteria are the factors that would make a study ineligible to be included. Criteria that should be considered include:
Type of studies: It is important to select articles with an appropriate study design for the research question. Dates for the studies and a timeline of the problem/issue being examined may need to be identified.
Type of participants: Identify the target population characteristics. It is important to define the target population's age, sex/gender, diagnosis, as well as any other relevant factors.
Types of intervention: Describe the intervention being investigated. Consider whether to include interventions carried out globally or just in the United States. Eligibility criteria for interventions should include things such as the dose, delivery method, and duration of the investigated intervention. The interventions that are to be excluded may also need to be described here.
Types of outcome measures: Outcome measures usually refer to measurable outcomes or ‘clinical changes in health’. For example, these could include body structures and functions like pain and fatigue, activities as in functional abilities, and participation or quality of life questionnaires.
A balance of specific inclusion and exclusion criteria is paramount. For some systematic reviews, there may already be a large pre-existing body of literature. The search strategy may retrieve thousands of results that must be screened. Having explicit exclusion criteria from the beginning allows those conducting the screening process, an efficient workflow. For the final product there should be a section in the review dedicated to 'Characteristics of excluded studies.' It is important to summarize why studies were excluded, especially if to a reader the study would appear to be eligible for the systematic review.
For example, a team is conducting a systematic review regarding intervention options for the treatment of opioid addiction. The research team may want to exclude studies that also involve alcohol addiction to isolate the conditions for treatment interventions solely for opioid addiction.
Before developing your inclusion/exclusion criteria, please read Chapter Three of the Cochrane Handbook that reviews considerations for developing this criteria.
You must have a selection of relevant articles (a max of 5). Review the articles and make a bullet point list for each study of why that study would be either included or excluded from the review. This exercise can help jump start your predefined inclusion and exclusion criteria. This should be done before you start the review.
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.
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.