Table 3

The criteria for the Grading of Recommendations Assessment, Development, and Evaluation approach to examine the overall certainty of evidence31

Study designQuality of evidenceLower certainty score ifHigher certainty score if
Randomised trialHighRisk of bias

  • 1 Serious

  • 2 Very serious


Inconsistency

  • 1 Serious

  • 2 Very serious


Indirectness

  • 1 Serious

  • 2 Very serious


Imprecision

  • 1 Serious

  • 2 Very serious


Publication bias

  • 1 Likely

  • 2 Very likely

Large effect
+1 Large
+2 Very large
  Dose–response
+1 evidence of a gradient
Moderate
  All plausible confounding would:
+1 Reduce a demonstrated effect
Observational studyLow
  +1 Suggest a spurious effect when results show no effect
 Very low