Table 2

GRADE system for grading recommendations

Strength of the recommendation	Quality of the evidence
1=strongly recommended 2=weakly recommended	A=high quality: RCT(s) B=moderate quality: downgraded RCT(s) or upgraded observational study(s) C=low quality: observational study(s) D=very low quality: downgraded observational study(s)
Factors determining the strength of recommendations: Balance between desirable and undesirable effects Quality of evidence Values and preferences Costs of the intervention	Factors that may decrease QoE: Study limitations Inconsistency of results Indirectness of evidence Imprecision Publication bias Factors that may increase QoE: Large magnitude of effect Plausible confounding factors would reduce any demonstrated effect Dose–response gradient

Strength of the recommendation

Quality of the evidence

1=strongly recommended
2=weakly recommended

A=high quality: RCT(s)
B=moderate quality: downgraded RCT(s) or upgraded observational study(s)
C=low quality: observational study(s)
D=very low quality: downgraded observational study(s)

Factors determining the strength of recommendations:

Balance between desirable and undesirable effects
Quality of evidence
Values and preferences
Costs of the intervention

Factors that may decrease QoE:

Study limitations
Inconsistency of results
Indirectness of evidence
Imprecision
Publication bias

Factors that may increase QoE:

Large magnitude of effect
Plausible confounding factors would reduce any demonstrated effect
Dose–response gradient

GRADE, Grading of Recommendations, Assessment, Development and Evaluations; QoE, quality of the evidence; RCT, randomised controlled trial.