Table 1

Levels of evidence and grading of recommendations for treatment1 2

Level of evidence:
 Level 1Data from randomised trials with low false positive (α) and low false negative (β) errors
 Level 2Data from randomised trials with high false positive (α) or high false negative (β) errors
 Level 3Data from randomised concurrent cohort studies
 Level 4Data from randomised cohort studies that use historical controls
 Level 5Data from anecdotal case series
Strength of treatment recommendations:
 Grade ASupported by level 1 evidence
 Grade BSupported by level 2 evidence
 Grade CSupported by level 3, 4, or 5 evidence