Grade Definitions and ChartThe interactive pie chart divides the Conclusion Statements currently in the EAL by Grades based on the strength of the evidence. Do you want to know which conclusion statements are Grade ? or Grade III? Simply click on the section of the graph corresponding to that grade.
Grades are assigned based on the evidence found through systematic reviews of published literature. For example, a determination that there is "Good" (Grade I) evidence that an intervention is effective means that there is good quality research to support the conclusion. However a determination that there is "insufficient evidence (Grade V) to determine effectiveness of a particular intervention does not mean that the intervention does not work but rather indicates that additional research is needed to determine whether or not the intervention is effective.
- Narrative Explanation of Grades
Narrative Explanation of Grades
Grade I: Good/Strong—The evidence consists of results from studies of strong design for answering the question addressed. The results are both clinically important and consistent with minor exceptions at most. The results are free of serious doubts about generalizability, bias, and flaws in research design. Studies with negative results have sufficiently large sample sizes to have adequate statistical power.
Grade II: Fair—The evidence consists of results from studies of strong design answering the question addressed, but there is uncertainty attached to the conclusion because of inconsistencies among the results from different studies or because of doubts about generalizability, bias, research design flaws, or adequacy of sample size. Alternatively, the evidence consists solely of results from weaker designs for the questions addressed, but the results have been confirmed in separate studies and are consistent with minor exceptions at most.
Grade III: Limited—The evidence consists of results from a limited number of studies of weak design for answering the questions addressed. Evidence from studies of strong design is either unavailable because no studies of strong design have been done or because the studies that have been done are inconclusive due to lack of generalizability, bias, design flaws, or inadequate sample sizes.
Grade IV: Expert Opinion Only—The support of the conclusion consists solely of the statement of informed medical commentators based on their clinical experience, unsubstantiated by the results of any research studies.
Grade V: Not Assignable—There is no evidence available that directly supports or refutes the conclusion.
- Table of Grading Criteria
Table of Grading Criteria
The Academy Expert Workgroup members use the following predefined criteria to grade the strength of the evidence supporting each conclusion statement. These criteria guide 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
Conclusion Grading Table Strength of Evidence Elements Grades I
Expert Opinion Only
Grade Not Assignable
Considers design and execution
Studies of strong design for question
Free from design flaws, bias and execution problems
Studies of strong design for question
with minor methodological concerns, OR
Only studies of weaker study design for question
Studies of weak design for answering the question
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
Of findings across studies
Findings generally consistent in direction and size of effect or degree of association, and statistical significance with minor exceptions at most 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 subjects in studies
One to 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 Clinical 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
Size of effect is small or lacks statistical and/or clinical significance
Objective data unavailable Indicates area for future research 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