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Overview of the GRADE system for grading the quality of evidence (Adapted from Reference[7]): A) Criteria for assigning grade of evidence; B) Definitions in grading the quality of evidence. |
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| A) |
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| Criteria for assigning level of evidence |
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| Type of Evidence |
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| Randomized trial |
High |
| Observational study |
Low |
| Any other type of research evidence |
Very low |
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| Increase level if: |
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| Strong association |
(+1) |
| Very strong association |
(+2) |
| Evidence of a dose response gradient |
(+1) |
| Plausible confounders reduced the observed effect |
(+1) |
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| Decrease level if: |
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| Serious or very serious limitations to study quality |
(-1) or (-2) |
| Important inconsistency |
(-1) |
| Some or major uncertainty about directness |
(-1) or (-2) |
| Imprecise or sparse data* |
(-1) |
| High probability of reporting bias |
(-1) |
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| B) |
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| Definitions for levels of evidence |
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| High |
Further research is not likely to change our confidence in the effect estimate |
| Moderate |
Further research is likely to have an important impact on our confidence in the estimate of effect and may change the estimate |
| Low |
Further research is very likely to have an important impact on our confidence in the estimate of effect and is likely to change the estimate |
| Very Low |
Any estimate of effect is uncertain |
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*Few outcome events or observations or wide confident limits around an effect estimate | |
Bagshaw and Bellomo Philosophy, Ethics, and Humanities in Medicine 2008 3:23 doi:10.1186/1747-5341-3-23 |
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