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Level of evidence and degree of recommendation.
| Level | Types of evidence | Degree of recommendation |
|---|---|---|
| 1a | Meta analyses, systematic reviews of RCTs/guideline/Cochrane systematic review | Strongly recommended/directly applicable |
| 1b | Systematic review with at least one RCTs | Highly recommended/directly applicable |
| 1c | RCTs | Recommended/applicable |
| 2a | Systematic reviews of case control or cohort studies | Extrapolated evidence fromother studies |
