Table 1.
Ranking of studies and clinical trials by their respective levels of evidence (LOE), as defined by the Oxford Centre for Evidence Based Medicine [60–62]
| Level of evidence | Study type |
|---|---|
| 1 | Systematic review of RCT |
| High-quality RCT | |
| 2 | Systematic review of cohort studies |
| Low-quality RCT | |
| Cohort studies/non-randomised controlled trial | |
| 3 | Systematic review of case–control studies |
| Case–control studies | |
| 4 | Case series |
| Low-quality case–control studies | |
| Low-quality cohort studies/non-randomised controlled trial | |
| 5 | Case reports |
| Expert opinions |