Table 1

ADA evidence-grading system for “Standards of Medical Care in Diabetes”

Level of evidenceDescription
AClear 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; i.e., “all or none” rule developed by the Centre for Evidence-Based Medicine at the University of 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
BSupportive 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
CSupportive 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 with historical controls)
 • Evidence from case series or case reports
Conflicting evidence with the weight of evidence supporting the recommendation
EExpert consensus or clinical experience