Type |
Strength |
I |
Strong evidence from at least one systematic review of multiple well-designed, randomized controlled trials. |
II |
Strong evidence from at least one properly designed, randomized controlled trial of appropriate size. |
III |
Evidence from well-designed trials without randomization, single group pre-post, cohort, time series, or matched case-control studies. |
IV |
Evidence from well-designed, non-experimental studies from more than one center or research group. |
V |
Opinions of respected authorities, based on clinical evidence, descriptive studies, or reports of expert committees. |