Table 1 Recommendation grading
| Level of scientific proof provided by the literature (for clinical studies) | Recommendation grading |
|---|---|
|
Level 1
High-power randomised comparative studies Meta-analysis of randomised comparative studies Decision analysis based on well-conducted studies |
A
Scientific proof established |
|
Level 2
Low-power randomised comparative studies Well-conducted non-randomised comparative studies Cohort studies |
B
Scientific proof presumed |
|
Level 3
Case–control studies |
C
Low level of proof |
|
Level 4
Comparative studies with major bias Retrospective studies Case series Descriptive epidemiological studies (cross-sectional, longitudinal) |