How to conduct a systematic review
If you are considering embarking on a systematic review, there are several issues you need to contemplate if you wish to conduct one. In healthcare, for example, the first step would be to define an explicit research question by using the PICOTS (Population, Intervention, Comparator, Outcome, Timing, Setting) framework, and also register the protocol for the review on PROSPERO, the international database of prospectively registered systematic reviews. Protocols provide a complete detailed description of the process by which the review will be conducted. Registering the protocol reduces research bias, duplication of effort, resource waste, and provides greater transparency. Outside of medical sciences, protocols can be uploaded to Open Science Framework.
You must adopt a comprehensive, objective and reproducible search strategy to capture all relevant sources of evidence. In doing so, you can be confident of having incorporated all the appropriate material for the topic at hand. A thorough search strategy should involve multiple databases, registries, sources of grey literature (link), conference proceedings and abstracts. Following the predefined eligibility criteria, you then need to analyze the screened search results to extract data from those publications that meet the inclusion criteria.
Don’t forget to assess the risk of bias when applicable (i.e., in clinical research). Ideally, these methodological steps should preferably be performed by two authors independently, one of which is a methodologist and the other a content area expert. Summarizing the results of the included studies and interpreting their findings in the light of certainty of evidence and their applicability are the final steps of completing a systematic review. You can also include a meta-analysis if applicable.
In order to assess the methodological quality of systematic reviews in biomedical sciences, checklists like the AMSTAR – A MeaSurement Tool to Assess systematic Reviews can be utilized. Lastly, the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) checklist, is a minimum set of items for reporting in systematic reviews: include one with your full article. The flow diagram can also be adopted to use for non-medical research (link).