Objective: To clarify the GRADE (grading of recommendations assessment, development and evaluation) definition of certainty of evidence and suggest possible approaches to rating certainty of the evidence for systematic reviews, health technology assessments and guidelines.
Study Design and Setting: This work was carried out by a project group within the GRADE Working Group, through brainstorming and iterative refinement of ideas, using input from workshops, presentations, and discussions at GRADE Working Group meetings to produce this document, which constitutes official GRADE guidance.
Results: Certainty of evidence is best considered as the certainty that a true effect lies on one side of a specified threshold, or within a chosen range. We define possible approaches for choosing threshold or range. For guidelines, what we call a fully contextualized approach requires simultaneously considering all critical outcomes and their relative value. Less contextualized approaches, more appropriate for systematic reviews and health technology assessments, include using specified ranges of magnitude of effect, e.g. ranges of what we might consider no effect, trivial, small, moderate, or large effects.
Conclusion: It is desirable for systematic review authors, guideline panelists, and health technology assessors to specify the threshold or ranges they are using when rating the certainty in evidence.

Original languageEnglish
Pages (from-to)4-13
Number of pages10
JournalJournal of Clinical Epidemiology
Early online date18 May 2017
Publication statusPublished - Jul 2017

Bibliographical note

The authors would like to thank colleagues at the Swedish Agency for Health Technology Assessment and Assessment of Social Services (SBU) who, through participating in a series of seminars, contributed with valuable input on the initial draft of the presented approaches. The authors also thank all GRADE Working Group members who have contributed to the paper during group discussions at Grade Working Group meetings.

The Health Services Research Unit, University of Aberdeen, receives core funding from the Chief Scientist Office of the Scottish Government Health Directorates. The Parker Institute, Bispebjerg and Frederiksberg Hospital is supported by a core grant from the Oak Foundation (OCAY-13-309). SVK is funded by a NRS Scottish Senior Clinical Fellowship (SCAF/15/02), the Medical Research Council (MC_UU_12017/13 & MC_UU_12017/15) and Chief Scientist’s Office (SPHSU13 & SPHSU15).


  • certainty of evidence
  • thresholds
  • guidelines
  • systematic reviews
  • health technology assessment


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