Table 2

Grading of Recommendations Assessment, Development and Evaluation system20

CodeQuality of evidenceDefinition
AHighFurther research is very unlikely to change our confidence in the estimate of effect.
• Several high-quality studies with consistent results
• In special cases: one large, high-quality multicentre trial
BModerateFurther research is likely to have an important impact on our confidence in the estimate of effect and may change the estimate.
• One high-quality study
• Several studies with some limitations
CLowFurther research is very likely to have an important impact on our confidence in the estimate of effect and is likely to change the estimate.
• One or more studies with severe limitations
DVery lowAny estimate of effect is very uncertain.
• Expert opinion
• No direct research evidence
• One or more studies with very severe limitations