Certainty of evidence grades
| Grade | Letter | Definition |
| High | A | We are very confident that the true effect lies close to that of the estimate of the effect |
| Moderate | B | We are moderately confident in the effect estimate: The true effect is likely to be close to the estimate of the effect, but there is a possibility that it is substantially different |
| Low | C | Our confidence in the effect estimate is limited: The true effect may be substantially different from the estimate of the effect. |
| Very low | D | We have very little confidence in the effect estimate: The true effect is likely to be substantially different from the estimate of effect |