Class of
Class IAlways acceptable, proven safe, definitely useful
Class IIaAcceptable, safe, useful (standard of care or intervention of choice)
Class IIbAcceptable, safe, useful (within the standard of care or an optional or alternative intervention)
Class indeterminatePreliminary research stage with promising results but insufficient available evidence to support a final class decision
Class IIIUnacceptable, no documented benefit, may be harmful

Clinical Interpretation of Classes of Recommendations