A systematic review is a thorough compilation and analysis of all known evidence on a given subject. In order to be formally recognised by publishers and repositories, a systematic review must include the following elements:
- A clearly defined research question and protocol
(research plan). The research question is often developed after performing preliminary research on the subject, ensuring that it is viable for a systematic review. You should also thoroughly search the literature to ensure no other systematic review already exists on your topic.
- Evidence of a rigorous search process. The reason why it is called a "systematic" review is because of the systematic search process that is required to uncover all of the evidence on a given subject. Systematic searching demands a carefully planned and thorough search strategy that will recall the maximum number of relevant results. For this reason, in addition to simply presenting search results, systematic reviews must include the exact search strategy used to find literature in each database.
- Inclusion and exclusion criteria. Not all evidence found during the search process will be relevant or appropriate for your research question. That is why it is important to clearly define the criteria you use to decide which studies should and should not be included in your analysis.
- Critical appraisal and bias assessment of all included studies. If a study is to be included in your review, the quality of its evidence must be critically appraised by each member of your research team. Additionally, because all studies carry an inherent risk of bias, studies should be thoroughly evaluated on their impartiality. This step ensures that your systematic review will represent the highest possible quality of evidence.
- An in-depth report outlining the process of finding and appraising literature, extracting data, measuring bias, and analysing results. Systematic review report guidelines can be found in many places, and are discussed in more detail here.
[1] Littell, J.H., Corcoran, J., & Pillai, V. (2008). Systematic Reviews and Meta-Analysis. Oxford University Press. Retrieved from http://www.oxfordscholarship.com/view/10.1093/acprof:oso/9780195326543.001.0001/acprof-9780195326543
[2] Image from the Cochrane Consumers and Communication Inforgraphics Page
(research plan). The research question is often developed after performing preliminary research on the subject, ensuring that it is viable for a systematic review. You should also thoroughly search the literature to ensure no other systematic review already exists on your topic.