Levels of evidence and grading of recommendations for treatment1 2
| Level of evidence: | |
| Level 1 | Data from randomised trials with low false positive (α) and low false negative (β) errors |
| Level 2 | Data from randomised trials with high false positive (α) or high false negative (β) errors |
| Level 3 | Data from randomised concurrent cohort studies |
| Level 4 | Data from randomised cohort studies that use historical controls |
| Level 5 | Data from anecdotal case series |
| Strength of treatment recommendations: | |
| Grade A | Supported by level 1 evidence |
| Grade B | Supported by level 2 evidence |
| Grade C | Supported by level 3, 4, or 5 evidence |