Table 2.

Custom system for assigning level of evidence and strength of recommendation.

Levels of Evidence		Strength of Recommendation
I	Metaanalyses, systematic reviews of RCT, or individual RCT	A	Strong recommendation: Direct level I evidence
II	Metaanalysis, systematic reviews of observational studies (cohort/case control studies), or individual observational studies	B	Moderate recommendation: Direct level II evidence or extrapolated level I evidence
	OR
	RCT subgroup/post-hoc analyses
III	Nonanalytic studies, e.g., case reports, case series	C	Weak recommendation Direct level III evidence or extrapolated level II evidence
IV	Expert opinion	D	Consensus recommendation: Expert opinion based on very limited evidence
NR	Recommendations are not linked to evidence