Table 1.

Evidence Levels and Recommendation Grades

Evidence levels	A	Further research is unlikely to change our confidence in the estimate of the effect.
	B	Further research is likely to have an important impact on our confidence in the estimate of the effect and may change the estimate.
	C	Further research is very likely to have an important impact on our confidence in the estimate of the effect and is likely to change the estimate.
Recommendation grades	Strong	The recommendation can apply to most patients in most circumstances. The desired effect is greater than the harmful effect.
	Weak	The best action may differ depending on circumstances or patient or society values. Other alternatives may be equally reasonable. The desired effect may be slightly larger than the harmful effect.