A final step of the systematic review and/or meta-analysis is to assess the certainty of evidence purported by your review.
This stage shares some characteristics with the critical appraisal phase, but is a separate, more robust appraisal and is described as its own phase in the systematic review. Sometimes this phase is also called referred to as assessing strength of recommendations, quality of evidence, or some combination thereof.
In the critical appraisal stage of the review, you're assessing the risk of bias in each included study. This phase, the assessment of certainty of evidence, takes the critical appraisal a step further by considering the overall quality or reliability of evidence purported by your review. As a result, your team will identify whether the evidence is strong or weak, or some variation of this. The ultimate intention of this stage is to translate the findings of your review to action.
Reflecting on the importance of this stage, the GRADE Working Group (a health-focused initiative) state that "Systematic reviews of the effects of healthcare provide essential, but not sufficient information for making well informed decisions. Reviewers and people who use reviews draw conclusions about the quality of the evidence, either implicitly or explicitly. Such judgments guide subsequent decisions. For example, clinical actions are likely to differ depending on whether one concludes that the evidence that blood thinners reduces the risk of stroke in patients with atrial fibrillation is convincing (high quality) or that it is unconvincing (low quality)."
The GRADE approach (Grading of Recommendations, Assessment, Development and Evaluation) is a method of grading the quality of evidence and the strength of recommendations in guidelines. This approach is being used by many international organisations to produce rigorous and transparent clinical practice guidelines and other health care recommendations.
Despite having been developed for health sciences in particular, GRADE is the most commonly referenced and used tool for assessing quality of evidence in systematic reviews and/or meta-analyses.
The GRADE Working Group "discourage the use of 'modified GRADE approaches' that differ from the approach described by the GRADE Working Group." With this in mind, they propose authors meet the following criteria to use GRADE:
If your evidence is qualitative, you may consider using the GRADE CERQual tool. Conceptually, this tool is similar to the standard GRADE, but is built to address qualitative evidence in particular.
The GRADEPro GDT web-application is available to help you conduct this analysis.
GRADE is not the only option, though it is most commonly referenced in the context of assessing certainty of evidence in systematic reviews and/or meta-analyses. There are many, very specific tools available to assess certainty of evidence. For example, the Strength of Recommendation Taxonomy (SORT): A Patient-Centered Approach to Grading Evidence in the Medical Literature.
If there is not a tool appropriate for your review, you should still reflect on the certainty of evidence through less formal means.
Chapter 14: Completing 'Summary of findings' tables and grading the certainty of evidence
...pre-specify any methods used to explore the possibility that the data identified are biased due to non-study related processes. Such bias may result from non-publication of studies (publication or dissemination bias) and the reporting of a subset of measured outcomes and analyses within studies (outcome reporting bias)...both publication bias and outcome reporting bias may affect meta-analyses, and the effect can be unpredictable
...summarize the confidence they have in the resulting body of evidence, ideally using an established and validated approach... plan for assessing the risk of bias across studies, inconsistency, imprecision, indirectness, publication bias, and factors that increase the confidence in an effect... for each outcome...in the PICO. The Grading of Recommendations Assessment, Development and Evaluation (GRADE) approach is increasingly recommended.