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Checklist to categorize level of evidence of study design
| Level of Evidence | Study Design |
| 1 | Experimental studies (eg, RCT with blinded allocation) |
| 2 | Quasi-experimental studies (eg, experimental study with randomization) |
| 3 | Controlled observational studies |
| 3a | Cohort studies |
| 3b | Case control studies |
| 4 | Observational studies without control groups |
| 5 | Expert opinion based on bench research or consensus |
