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Levels of Evidence
| I | Evidence obtained from high-quality diagnostic studies, prospective studies, randomized controlled trials, or systematic reviews |
| II | Evidence obtained from lesser-quality diagnostic studies, prospective studies, systematic reviews, or randomized controlled trials (eg, weaker diagnostic criteria and reference standards, improper randomization, no blinding, less than 80% follow-up) |
| III | Case-control studies or retrospective studies |
| IV | Case series |
| V | Expert opinion |
