Evidence-based medicine: Evidence

Evidence-based medicine: Evidence

Levels of Evidence

Ia From systematic review of meta-analyses of RCT’s

Ib From at least one RCT

IIa From at least one well-designed controlled study without randomisation

IIb From at least one other type of well-designed quasi-experimental study

III From well-designed non-experimental descriptive studies eg comparative- , correlation- and case-studies

IV From expert committee reports or opinions and/or clinical experience of respected authorities

Grades of Evidence

A At least one RCT as part of a body of literature of overall good quality and consistency addressing the specific recommendation (evidence levels Ia and Ib)

B Well-conducted clinical studies but no RCT’s on the topic of recommendation (evidence levels Ia and Ib)

C Expert committee reports or opinions and/or clinical experience of respected authorities. This grading indicates that directly applicable clinical studies or good quality are absent (evidence level IV)