GRADE guidelines 33: Addressing imprecision in a network meta-analysis.

Abstract Objective This article describes GRADE guidance for assessing imprecision when rating the certainty of the evidence from network meta-analysis. Study Design and Setting A project group within the GRADE working group conducted iterative discussions, computer simulations, and presentations at GRADE working group meetings to produce and obtain approval for this guidance. Results When addressing imprecision of a network estimate, reviewers should consider the 95% confidence or credible interval, and the optimal information size. If the 95% confidence or credible interval crosses a pre-specified threshold, reviewers should rate down the certainty of the evidence. If the 95% confidence interval does not cross any pre-specfied threshold, reviewers should consider the optimal information size. Because addressing the optimal information size may be challenging, reviewers can use the effect size to decide if any calculations are necessary. When the size of the effect is modest or the optimal information size is met, reviewers should not rate down for imprecision. Conclusion Reviewers should use this guidance when to appropriately address imprecision in the context of the assessment of certainty of evidence from network meta-analysis.