Literature Review: GRADE System

The Grades of Recommendation, Assessment, Development and Evaluation (GRADE) for Systematic Reviews

“GRADE defines the quality of a body of evidence as the extent to which one can be confident that an estimate of effect or association is close to the quantity of specific interest.”¹

The GRADE system entails an assessment of the quality of a body of evidence for five factors:

• Within-study risk of bias (methodological quality)
• Directness of evidence
• Heterogeneity (any kind of variability among studies)
• Precision of effect estimates
• Risk of publication bias

Levels of quality of a body of evidence in the GRADE approach

The highest quality rating is for randomized trial evidence.

• Randomized trial evidence can be downgraded  to moderate, low, or very low quality, depending on limitations, e.g.:
  • Randomization sequence was not concealed from the clinicians and researchers
  • The people involved in the study discovered which treatments were given to which patients
  • Over 50% of their patients were lost for follow-up
• Conversely, observational studies may be upgraded if they produce large effects with no obvious bias

Information Sources:

• ¹Cochrane Handbook for Systematic Reviews of Interventions:
  http://handbook.cochrane.org/chapter_12/12_2_assessing_the_quality_of_a_body_of_evidence.htm
• Introduction to evidence Based Practice, Duke University Medical Center Library
  http://guides.mclibrary.duke.edu/ebmtutorial