Level
|
Type of evidence
|
Ia | Evidence obtained from meta-analysis of randomised controlled trials |
Ib | Evidence obtained from at least one randomised controlled trial |
IIa | Evidence obtained from at least one well designed controlled study without randomisation |
IIb | Evidence obtained from at least one other type of well designed quasi-experimental study |
III | Evidence obtained from well designed non-experimental descriptive studies such as comparative studies, correlation studies, and case controlled studies |
IV | Evidence obtained from expert committee reports of opinions and/or clinical experiences of respected authorities |
| |
Grade
|
Type of recommendations
|
A (levels Ia, Ib) | Requires at least one randomised controlled trial as part of a body of literature of overall good quality and consistency addressing the specific recommendation |
B (levels IIa, IIb, III) | Requires availability of well conducted clinical studies but no randomised clinical trials on the topic of recommendation |
C (level IV) | Requires evidence from expert committee reports or opinions and/or clinical experience of respected authorities. Indicates absence of directly applicable studies of good quality |