Evidence Levels
| Level . | Definition . |
|---|---|
| 1 | RCTs or meta-analyses of multiple clinical trials with substantial treatment effects |
| 2 | RCTs with smaller or less significant treatment effects |
| 3 | Prospective, controlled, nonrandomized, cohort studies |
| 4 | Historic, nonrandomized, cohort or case-control studies |
| 5 | Case series: patients compiled in serial fashion, lacking a control group (excluded from review) |
| 6 | Animal studies or mechanical model studies (excluded from review) |
| 7 | Extrapolations from existing data collected for other purposes, theoretical analyses (excluded from review) |
| 8 | Rational conjecture (common sense); common practices accepted before evidence-based guidelines (excluded from review) |
| Level . | Definition . |
|---|---|
| 1 | RCTs or meta-analyses of multiple clinical trials with substantial treatment effects |
| 2 | RCTs with smaller or less significant treatment effects |
| 3 | Prospective, controlled, nonrandomized, cohort studies |
| 4 | Historic, nonrandomized, cohort or case-control studies |
| 5 | Case series: patients compiled in serial fashion, lacking a control group (excluded from review) |
| 6 | Animal studies or mechanical model studies (excluded from review) |
| 7 | Extrapolations from existing data collected for other purposes, theoretical analyses (excluded from review) |
| 8 | Rational conjecture (common sense); common practices accepted before evidence-based guidelines (excluded from review) |