ADA Evidence Grading System
Category/Grade Definition
A Clear evidence from well-conducted, generalizable, randomized
controlled trials that are adequately powered, including :
• Evidence from a well-conducted multicenter trial
• Evidence from a meta-analysis that incorporated quality ratings
in the analysis
Compelling nonexperimental evidence—ie, "all or none" rule developed
by Center for Evidence Based Medicine at Oxford
Supportive evidence from well-conducted randomized controlled trials
that are adequately powered, including :
• Evidence from a well-conducted trial at one or more institutions
• Evidence from a meta-analysis that incorporated quality ratings
in the analysis
B Supportive evidence from well-conducted cohort studies
• Evidence from a well-conducted prospective cohort study or registry
• Evidence from a well-conducted meta-analysis of cohort studies
• Supportive evidence from a well-conducted case-control study
C Supportive evidence from poorly controlled or uncontrolled studies
• Evidence from randomized clinical trials with one or more major or
three or more minor methodological flaws that could invalidate the
results
• Evidence from observational studies with high potential for bias (such
as case series with comparison to historical controls)
• Evidence from case series or case reports
Conflicting evidence with the weight of evidence supporting the
recommendation
E Expert consensus or clinical experience
From: http://professional.diabetes.org/nutrition
