Table 1.

Evidence classes and recommendation levels

Evidence
Class I	Prospective randomized blinded trial (PRBT) or review of PRBTs
Class II	Prospective matched pair cohort studies
Class III	Any controlled trial (incl. retrospective controls)
Class IV	Uncontrolled studies, case series, case reports, expert opinions
Recommendation
Level A	One class I or at least two class II studies
Level B	One class II or overwhelming class III evidence
Level C	At least two class III studies
“Good practice point”	Only class IV evidence