ebm

evidence based medicine (EBM)

Level I: Evidence obtained from at least one properly designed randomized controlled trial.
Level II-1: Evidence obtained from well-designed controlled trials without randomization.
Level II-2: Evidence obtained from well-designed cohort or case-control analytic studies, preferably from more than one center or research group.
Level II-3: Evidence obtained from multiple time series with or without the intervention. Dramatic results in uncontrolled trials might also be regarded as this type of evidence.
Level III: Opinions of respected authorities, based on clinical experience, descriptive studies, or reports of expert committees.

class I	evidence &/or general agreement that Rx or procedure is beneficial, useful and effective
class II	conflicting evidence or opinion regarding usefulness or effectiveness
class IIa	weight of evidence is in favour of usefulness or effectiveness
class IIb	usefulness or effectiveness is less well established
class III	not recommended as evidence or opinion suggests NOT useful or effective, and may cause harm