Quality of Evidence Assessment: Grading of Recommendations Assessment, Development and Evaluation (modified GRADE) Process*

CodeQuality of EvidenceDefinition
A High

We are very confident that the true association between the factor and the clinical effect lies close to the reported estimates.  Further research is very unlikely to change our confidence in the association.

  • Several high-quality studies with consistent results
  • In special cases: one large, high-quality multi-centre trial
B Moderate

We are moderately confident that the true association between the factor and the clinical effect lies close to the reported estimates, but there is a possibility that it is substantially different. Further research is likely to have an important impact on our confidence in the estimated association.

  • One high-quality study
  • Several studies with some limitations
C Low

Our confidence in the estimated association between the factor and the clinical effect is limited and the true association may not lie close to the reported estimates. Further research is very likely to have an important impact on our confidence in the estimate of any possible association.

  • One or more studies with severe limitations
D Very Low

We have very little confidence in the estimates of an association between the factor and the clinical effect.  If an association exists, it is likely to be substantially different from the current estimates.

  • Expert opinion
  • No direct research evidence
  • One or more studies with very severe limitations

* Balshem H, Helfand M, Schunemann HJ et al. GRADE guidelines: 3. Rating the quality of evidence. J Clin Epidemiol. 2011;64(4):401-406.