Table 2.

Relation Between Levels of Evidence and Grades of Recommendations

Level of EvidenceRecommendation
Level I: Large randomized trials with clearcut results (and low risk of error)Grade A
Level II: Small randomized trials with uncertain results (and moderate to high risk of error)Grade B
Level III: Nonrandomized, contemporaneous controlsGrade C
Level IV: Nonrandomized, historical controlsGrade C
Level V: No controls; case series onlyGrade C