Table I.

Grading evidences and recommendations (adapted from the GRADE system).

Quality of evidence
A - High	Further 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
B - Moderate	Further 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
C - Low	Further 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
D - Very low	Any estimate of effect is very uncertain. Expert opinion No direct research evidence One or more studies with very severe limitations
Strenght of recommendation
1 - Strong	Factors influencing the strength of the recommendation included the quality of evidence, presumed patient-important outcomes, and cost.
2 - Weak	Variability in preferences and values, or more uncertainty: more likely a weak recommendation is warranted. Recommendation is made with less certainty: high cost or resource consumption