Level of evidence and strength of recommendation.22-24
| Level | Strength | Level | Description |
|---|---|---|---|
| Level I high degree of certainty | Standard | A | Based on consistent class I evidence (well-designed RCT) |
| B | Single class I study or consistent class II evidence (especially when circumstances preclude RCTS) | ||
| Level II moderate degree of certainty | Guideline | C | Class II evidence (less well-designed RCT or one or more observational study) or a preponderance of class III evidence |
| Level III unclear degree of certainty | Option | D (or I) | Class III evidence (case series, case reports, and expert opinion) |