Development of living evidence-informed guidelines, part 4: Rationale and methodology for conducting systematic reviews to inform guidelines

Background: Systematic reviews (SRs) support guideline development by means of synthesizing available evidence for each aspect that must be considered when formulating recommendations. The authors consolidated standard methodology to ensure rigor, transparency, and reproducibility throughout the review process. Type of Studies Reviewed: The body of evidence addressing methodological aspects for the rationale and conduct of SRs to support living evidence-informed clinical and public health guidelines was included. The most up-to-date versions of methodological handbooks and articles presenting SR methodology were selected. Results: Various types of SRs can inform guidelines, such as intervention, diagnostic, prognostic, and cost-effectiveness reviews. Although core steps in the review process are common across SR types, methodological adaptations are often required, depending on the review type (eg, tools for assessing risk of bias and methods for analyzing and synthesizing the evidence). The certainty of the evidence should be assessed using the Grading of Recommendations Assessment, Development and Evaluation guidance appropriate to the specific question type. Conclusions and Practical Implications: SRs create the foundation for formulating clinical and public health recommendations within guidelines, but SRs are not sufficient on their own. Additional factors must also be considered to ensure that recommendations are appropriate and implementable.