Levels of evidence | Â |
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Ia | Evidence from a systematic review or meta-analysis of randomized controlled trials (RCT’s) |
Ib | Evidence from at least one RCT |
IIa | Evidence from at least one well-designed controlled study without randomization |
IIb | Evidence from at least one well-designed quasi-experimental study, such as a cohort study |
III | Evidence from a well-designed non-experimental descriptive studies, such as comparative studies, correlation studies, case–control studies and case series |
IV | Expert committee reports, opinions and/or clinical experience of respected authorities |