GRADE guidance 35: update on rating imprecision for assessing contextualized certainty of evidence and making decisions

Abstract

Objectives: Grading of Recommendations Assessment, Development and Evaluation (GRADE) guidance to rate the certainty domain of imprecision is presently not fully operationalized for rating down by two levels and when different baseline risk or uncertainty in these risks are considered. In addition, there are scenarios in which lowering the certainty of evidence by three levels for imprecision is more appropriate than lowering it by two levels. In this article, we conceptualize and operationalize rating down for imprecision by one, two and three levels for imprecision using the contextualized GRADE approaches and making decisions.

Methods: Through iterative discussions and refinement in online meetings and through email communication, we developed draft guidance to rating the certainty of evidence down by up to three levels based on examples. The lead authors revised the approach according to the feedback and the comments received during these meetings and developed GRADE guidance for how to apply it. We presented a summary of the results to all attendees of the GRADE Working Group meeting for feedback in October 2021 (approximately 80 people) where the approach was formally approved.

Results: This guidance provides GRADE's novel approach for the considerations about rating down for imprecision by one, two and three levels based on serious, very serious and extremely serious concerns. The approach includes identifying or defining thresholds for health outcomes that correspond to trivial or none, small, moderate or large effects and using them to rate imprecision. It facilitates the use of evidence to decision frameworks and also provides guidance for how to address imprecision about implausible large effects and trivial or no effects using the concept of the 'review information size' and for varying baseline risks. The approach is illustrated using practical examples, an online calculator and graphical displays and can be applied to dichotomous and continuous outcomes.

Conclusion: In this GRADE guidance article, we provide updated guidance for how to rate imprecision using the partially and fully contextualized GRADE approaches for making recommendations or decisions, considering alternate baseline risks and for both dichotomous and continuous outcomes.

Keywords: GRADE; Guidelines; Health technology assessment; Imprecision; Statistical significance; Systematic reviews.