Table 1.
Criteria for assigning a level of evidence rating
| Level of evidence | Rating | Criteria |
|---|---|---|
| Strong | +++ or − − − | Consistent findings in multiple studies of good methodological quality, or in one study of excellent methodological quality |
| Moderate | ++ or − − | Consistent findings in multiple studies of fair methodological quality, or in one study of good methodological quality |
| Limited | + or − | Evidence from one study of fair methodological quality |
| Inconclusive | +/− | Inconclusive evidence |
| Unknown | ? | Only studies of poor methodological quality |