|
Ia |
Evidence obtained from meta-analysis or systematic reviews of randomized controlled trials. |
|
Ib |
Evidence obtained from at least one randomized controlled trial. |
|
IIa |
Evidence obtained from at least one well-designed controlled study without randomization. |
|
IIb |
Evidence obtained from at least one other type of well-designed quasi-experimental study, without randomization. |
|
III |
Evidence obtained from well-designed non-experimental descriptive studies, such as comparative studies, correlation studies and case studies. |
|
IV |
Evidence obtained from expert committee reports or opinions and/or clinical experiences of respected authorities. |
Adapted from “Annex B: Key to evidence statements and grades of recommendations,” by the Scottish Intercollegiate Guidelines Network (SIGN), 2012, in SIGN 50: A Guideline Developer’s Handbook. Available from http://www.sign.ac.uk/guidelines/fulltext/50/annexb.html