Table 1

Evidence categories for ACSM and evidence-grading system for clinical practice recommendations for ADA

I. ACSM evidence categories
Evidence categorySource of evidenceDefinition
ARandomized, controlled trials (overwhelming data)Provides a consistent pattern of findings with substantial studies
BRandomized, controlled trials (limited data)Few randomized trials exist, which are small in size, and results are inconsistent
CNonrandomized trials, observational studiesOutcomes are from uncontrolled, nonrandomized, and/or observational studies
DPanel consensus judgmentPanel's expert opinion when the evidence is insufficient to place it in categories A through C
II. ADA evidence-grading system for clinical practice recommendations
Level of evidenceDescription
AClear evidence from well-conducted, generalizable, randomized, controlled trials that are adequately powered, including the following:
  • Evidence from a well-conducted multicenter trial

  • Evidence from a meta-analysis that incorporated quality ratings in the analysis

Compelling nonexperimental evidence, i.e., the “all-or-none” rule developed by the Centre for Evidence-Based Medicine at Oxford
Supportive evidence from well-conducted, randomized, controlled trials that are adequately powered, including the following:
  • 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, including the following:
  • 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, including the following:
  • 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
EExpert consensus or clinical experience