| A |
Evidence from well-conducted, generalizable randomized controlled trials that are adequately powered, including |
| - Evidence from well-conducted multicenter trials |
| - Evidence from meta-analyses that incorporated quality ratings in the analysis |
| B |
Evidence from well-conducted cohort studies |
| - Evidence from well-conducted prospective cohort studies or registries |
| - Evidence from well-conducted meta-analyses of cohort studies |
| - Evidence from well-conducted case-control studies |
| C |
Evidence from poorly controlled or uncontrolled studies |
| - Evidence from randomized controlled studies with some flaws in design, method, or analysis |
| - Evidence from case reports |
| - Evidence from observational studies with potential bias |
| E |
Expert consensus |
