The grades of evidence (I-III) and levels of recommendation (A-C) are defined at the end of the "Major Recommendations" field.
The following recommendations are based on good and consistent scientific evidence (Level A):
The following recommendations are based on limited and inconsistent scientific evidence (Level B):
The following recommendations are based primarily on consensus and expert opinion (Level C):
Grades of Evidence
I: Evidence obtained from at least one properly designed randomized controlled trial.
II-1: Evidence obtained from well-designed controlled trials without randomization.
II-2:Evidence obtained fromwell-designed cohort or case–control analytic studies, preferably from more than one center or research group.
II-3:Evidence obtained from multiple time series with or without the intervention. Dramatic results in uncontrolled experiments also could be regarded as this type of evidence.
III: Opinions of respected authorities, based on clinical experience, descriptive studies, or reports of expert committees.
Levels of Recommendations
Level A — Recommendations are based on good and consistent scientific evidence.
Level B — Recommendations are based on limited or inconsistent scientific evidence.
Level C — Recommendations are based primarily on consensus and expert opinion.