Table 1 Summary of a simplified evidence hierarchy, A) Levels of evidence across clinical research studies, and B) Grading of recommendations based on levels of evidence (Adapted from [2, 3])
From: The need to reform our assessment of evidence from clinical trials: A commentary
A) | Â |
|---|---|
Levels of Evidence | |
Level I | Well conducted, suitably powered RCT |
Level II | Well conducted, but small and under powered RCT |
Level III | Non-randomized observational studies |
Level IV | Non-randomized study with historical controls |
Level V | Case series without controls |
B) | Â |
Grades of Recommendations | |
Grade A | Level I |
Grade B | Level II |
Grade C | Level III or lower |