| I |
Evidence of at least one large randomised controlled trial (RCT) of good methodological quality (low potential for bias) or meta-analyses of well-conducted randomised clinical trials without heterogeneity |
| II |
RCTs * small or large RCTs * with suspicion of bias (low methodological quality) or meta-analyses of these tests or tests with demonstrated heterogeneity |
| III |
Prospective cohort studies |
| IV |
Retrospective cohort studies or case-control studies |
| V |
Studies without a control group, case reports, and expert opinions |
| * RCTs = Randomised clinical trials |
| B) Strength of recommendation |
| A |
Solid evidence of efficacy with substantial clinical advantage—strongly recommended |
| B |
Strong or moderate evidence, in terms of effectiveness, but with a limited clinical benefit—generally recommended |
| C |
Insufficient evidence of effectiveness or benefit does not outweigh the risks/disadvantages (i.e., adverse events or costs)—optional |
| D |
Moderate evidence against effectiveness or evidence indicating adverse outcomes—generally not recommended |
| E |
Strong evidence against effectiveness or indicating adverse outcomes—not recommended |
