The GRADE approach and Bradford Hill's criteria for causation

Abstract

This article describes how the Grading of Recommendations Assessment, Development and Evaluation (GRADE) approach to grading the quality of evidence and strength of recommendations considers the Bradford Hill criteria for causation and how GRADE may relate to questions in public health. A primary concern in public health is that evidence from non-randomised studies may provide a more adequate or best available measure of a public health strategy's impact, but that such evidence might be graded as lower quality in the GRADE framework. GRADE, however, presents a framework that describes both criteria for assessing the quality of research evidence and the strength of recommendations that includes considerations arising from the Bradford Hill criteria. GRADE places emphasis on recommendations and in assessing quality of evidence; GRADE notes that randomisation is only one of many relevant factors. This article describes how causation may relate to developing recommendations and how the Bradford Hill criteria are considered in GRADE, using examples from the public health literature with a focus on immunisation.