Meta-analysis has become a common approach to summarize genetic association with the tremendous amount of published epidemiological evidence. Assessing the credibility of meta-analysis evidence on genetic association is a rapidly growing challenge. This paper illuminates how to assess the credibility of meta-analysis evidence by using Venice criteria. A semi-quantitative index assigns three levels for the amount of evidence, replication and protection from bias. At the end, three considerations are merged into a grading scheme, which generates three composite assessments: weak, moderate or strong. Credibility assessment is necessary to estimate whether a true genetic association exists. Such method provides indication for further study and is of clinical importance.
Network meta-analysis (NMA) is a method that can compare and rank the effects of different interventions, which plays an important role in evidence translation and evidence-based decision-making. In 2014, the GRADE working group first introduced the GRADE method for NMA evidence certainty grading. Since then, its method system has been gradually supplemented and improved. In recent years, the GRADE working group has further improved the methods for evaluating intransitivity and imprecision in NMA, and has made recommendations for the presentation and interpretation of NMA results, forming a complete methodological chain of NMA evidence certainty grading and result interpretation consisting of 6 steps. Our team updated the method system of GRADE applied in NMA with specific cases to provide references for relevant researchers.