Levels of evidence.*
| *The PED designation indicates the evidence is limited to studies in the pediatric patient population | |
| I | Evidence obtained from at least one properly designed randomized controlled trial |
| II-1 | Evidence obtained from well-designed controlled trials without randomization |
| II-2 | Evidence obtained from well-designed cohort or case- control analytic studies, preferably from more than one center or research group |
| II-3 | Evidence obtained from multiple time series with or without the intervention. Dramatic results in uncontrolled experiments also could be regarded as this type of evidence |
| III | Opinions of respected authorities, based on clinical experience, descriptive studies, or reports of expert committees |
| *The PED designation indicates the evidence is limited to studies in the pediatric patient population | |
| I | Evidence obtained from at least one properly designed randomized controlled trial |
| II-1 | Evidence obtained from well-designed controlled trials without randomization |
| II-2 | Evidence obtained from well-designed cohort or case- control analytic studies, preferably from more than one center or research group |
| II-3 | Evidence obtained from multiple time series with or without the intervention. Dramatic results in uncontrolled experiments also could be regarded as this type of evidence |
| III | Opinions of respected authorities, based on clinical experience, descriptive studies, or reports of expert committees |