Updated guidelines: Classes of Recommendations and levels of evidence

1
Updated guidelines Classes of Recommendations
and levels of evidence
VBWG
Classes
Levels of evidence
I Intervention is useful and effective
A Data derived from multiple randomized
clinical trials
IIA Evidence conflicts / opinions differ, but
leans toward efficacy
B Data derived from a single RCT or
nonrandomized studies
IIB Evidence conflicts / opinions differ, but
leans against efficacy
C Consensus opinion of experts
III Intervention is not useful or effective and
may be harmful
Gibbons RJ et al. J Am Coll Cardiol.
200341159-68.