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Table 2
Recommendation grades and scientific level of evidence according to the HAS [1].
| Recommendations grade | Scientific level of proof from literature |
|---|---|
| A Well established proof |
Level 1 |
| High power randomized comparative trials; | |
| Meta-analysis of randomized comparative trials; | |
| Analysis of well conducted studies. | |
| B Scientific presumption |
Level 2 |
| Low power randomized comparative trials; | |
| Not randomized well conducted comparative studies; | |
| Cohort studies. | |
| C | Level 3 |
| Case-control studies. | |
| Low scientific proof | Level 4 |
| Comparative trials with number of bias; | |
| Retrospective studies; | |
| Case series; | |
| Descriptive epidemiological studies (transversal, longitudinal). | |
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