Table 1. Recommendation grades and evidence levels in evidence-based medicine^*1.

Recommendation grade	Definition
I	Evidence or general agreement that a type of treatment or diagnostic measure is effective, useful, or beneficial
II	Conflicting evidence and/or conflicting expert opinion as to the usefulness/effectiveness of a type of treatment or diagnostic measure
IIa	The evidence and expert opinion favor the usefulness and effectiveness of the measure in question
IIb	The usefulness and effectiveness of the measure in question are less well supported by the evidence and expert opinion
Evidence level	Definition
A	The recommendation is supported by at least two randomized studies
B	The recommendation is supported by a single randomized study and/or a meta-analysis of nonrandomized studies
C	Expert consensus based on studies and clinical experience

^*1 Modified from (2)