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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]) |
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| A) |
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| Levels of Evidence |
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| 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 |
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| B) |
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| Grades of Recommendations |
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| Grade A |
Level I |
| Grade B |
Level II |
| Grade C |
Level III or lower |
Bagshaw and Bellomo Philosophy, Ethics, and Humanities in Medicine 2008 3:23 doi:10.1186/1747-5341-3-23 |
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