A protocol outlines your objectives, planned methodology, and eligibility criteria. Developing and publishing a prospective protocol is considered a best practice in conducting a systematic review. Publishing an a priori protocol is a requirement for many publishers and a recommendation of others. Additionally, publishing a complete protocol provides the authors with a set of guidelines to follow while working on the initial review and facilitates reliable reproducibility post-publication.
Note: elements may vary by discipline
Eligibility criteria (also known as inclusion/exclusion criteria) for a systematic review should be established before beginning your review. Eligibility criteria may include the types of studies most relevant for answering your research question. For clinical fields, you may also want to define the population you are working with and include specifics in your eligibility criteria related to the population data.
You should be able to clearly defend your reason for establishing all of your eligibility criteria. While it may be tempting to limit by date or by peer review, this can introduce an element of bias into your methodology. Instead of including only peer reviewed articles, consider empirical studies as an eligibility criteria.
If you plan to exclude older papers that may not be as relevant to your research question, think about why a particular date may be relevant. For example, was a technique, technology, or theory essential to your research question developed in a certain year? This would provide defensible grounds for excluding papers written before that year.
Tip: Review existing systematic reviews and protocols on topics similar to yours to see what types of eligibility criteria other authors are using. This can guide you in developing your own.
Examples of eligibility criteria may include:
This guide was adapted from Systematic Reviews by University of Texas Libraries (https://guides.lib.utexas.edu/systematicreviews) which is licensed under a Creative Commons Attribution-NonCommercial 2.0 Generic License.