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Conclusion Grading Chart (Nutrition Education)

The 2010 Dietary Guideline Advisory Committee approved the use of the following predefined criteria to grade the strength of the evidence supporting each conclusion statement. These criteria guided members to carefully evaluate the:
  • quality of studies (both strength of design and execution),
  • quantity of studies and subjects,
  • consistency of findings across studies,
  • the magnitude of effect,
  • generalizability of findings
reported in the body of literature supporting each conclusion. The chart below was used by the 2010 Dietary Guidelines Advisory Committee and defines the criteria used to determine each grade.
DGAC Conclusion Grading Chart used to evaluate the strength of the body of evidence supporting conclusion statements

 
Elements

Strong

Moderate Limited Expert Opinion Only Grade Not Assignable
Quality
  • Scientific rigor and validity
  • Study design and execution
Studies of strong design

Free from design flaws, bias, and execution problems
Studies of strong design with minor methodological concerns
OR only studies of weaker study design for question

Studies of weak design for answering the question OR inconclusive findings due to design flaws, bias, or execution problems
No studies available

Conclusion based on usual practice, expert consensus, clinical experience, opinion, or extrapolation from basic research
No evidence that pertains to question being addressed
Consistency
  • Consistency of findings across studies
Findings generally consistent in direction and size of effect or degree of association, and statistical significance with minor very exceptions Inconsistency among results of studies with strong design,
OR consistency with minor exceptions across studies of weaker design
Unexplained inconsistency among results from different studies,
OR single study unconfirmed by other studies
Conclusion supported solely by statements of informed nutrition or medical commentators NA
Quantity
  • Number of studies
  • Number of study participants
One large study with a diverse population or several good quality studies
Large number of subjects studied
Studies with negative results have sufficiently large sample size for adequate statistical power
Several studies by independent investigators
Doubts about adequacy of sample size to avoid Type I and Type II error
Limited number of studies
Low number of subjects studied and/or inadequate sample size within studies
 
Unsubstantiated by published research studies Relevant studies have not been done
Impact
  • Importance of studied outcomes
  • Magnitude of effect
Studied outcome relates directly to the question
Size of effect is clinically meaningful
Significant (statistical) difference is large
Some doubt about the statistical or clinical significance of the effect Studied outcome is an intermediate outcome or surrogate for the true outcome of interest
OR size of effect is small or lacks statistical and/or clinical significance
Objective data unavailable Indicates area for future research
Generalizability
  • Generalizability to population of interest
Studied population, intervention and outcomes are free from serious doubts about generalizability Minor doubts about generalizability Serious doubts about generalizability due to
narrow or different study population, intervention or outcomes studied
Generalizability limited to scope of experience NA

Criteria adapted from the American Dietetic Association Evidence Analysis Library® and based upon: Greer N, Mosser G, Logan G, Wagstrom Halaas G. A practical approach to evidence grading. The Joint Commission Journal on Quality Improvement. 2000;26:700-712. Explanation of Grades and Grading Chart
 

Last Updated: 06/04/2014