Table 1 The hierarchy of evidence from the center for evidence-based-medicine
From: Italian guidelines for the management and treatment of neonatal cholestasis
Level | Definition |
|---|---|
1a | Systematic review (with homogeneity) of randomized clinical trials (RCTs) |
1b | Individual RCT (with narrow confidence interval) |
2a | Systematic review (with homogeneity) of cohort studies |
2b | Individual cohort study |
3a | Systematic review (with homogeneity) of case–control studies |
3b | Individual case–control study |
4 | Case-series (and poor quality cohort and case–control studies) |
5 | Expert opinion without explicit critical appraisal, or based on physiology, bench research or “first principles” |