Table 1

GRADE method for rating up or down the quality of evidence20

Study designQuality of evidenceLower ifHigher if
Randomised trial →HighRisk 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
All plausible confounding
+1 Would reduce a demonstrated effect or
+1 Would suggest a spurious effect when results show no effect
Moderate
Observational study →Low
Very low
  • GRADE, Grading of Recommendations Assessment, Development and Evaluation.