The following shows the Five Steps to Conducting a Systematic Review reproduced from the paper by Khan et. al.
Khan, K. S., Kunz, R., Kleijnen, J., & Antes, G. (2003). Five steps to conducting a systematic review. Journal of the Royal Society of Medicine, 96(3), 118-121. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC539417/
(1) Framing questions for a review
Questions should always be
Usually, a protocol for a systematic review (plan or set of steps to be followed in a study) will only be modified if it becomes clear that there are alternative ways of defining your population, intervention, outcomes or study designs.
(2) Identifying relevant work
Involves extensive searching of a wide range of online or print resources (e.g., MEDLINE, Embase, The Cochrane Library,etc. ) without language restrictions.
How to identify what studies to keep and what to reject?
[Useful article: Selecting Studies for Systematic Review: Inclusion and Exclusion Criteria]
(3) Assessing the quality of the studies
Note that study quality assessment is relevant to every step of a review.assessment. For example, Question formulation (Step 1) and study selection criteria (Step 2) should describe the minimum acceptable level of design.
Studies included in the review should be subjected to quality assessment using the critical appraisal guides and design-based quality checklists (refer to the Critical Appraisal tab). Quality assessment is used to:
(4) Summarizing the evidence
(5) Interpreting the findings
Check for any possible risk of bias
Check heterogeneity to help you determine if your overall summary can be trusted. If you have doubts, then check the effects observed in high-quality studies to help generate inferences.
Grade recommendations by reference to the strengths and weaknesses of the evidence