Table 5.

Evidence Grades Based on the Quality of Evidence⁸

Grade	Recommendation	Criteria and Strength of Recommendation
A	Strong	High-quality studies (level I) with moderate to substantial benefit/harm—“must/should” or “must not/should not”
B	Moderate	High-quality studies (level I) with slight benefit/harm OR acceptable-quality studies (level II) for moderate benefit/harm—“should” or “should not”
C	Weak	Acceptable-quality studies (level II) for slight benefit/harm OR low-quality studies (level III) for substantial benefit/harm—“may” or “may not”
Best Practice	Best Practice	Based on current clinical norms or expert opinion