Levels of quality and definition of a body of evidence in the Grading of Recommendation Assessment Development and Evaluation (GRADE) approach31,62,63.
| Underlying Methodology | Quality of Rating or Grade | Definition |
|---|---|---|
| Randomized trials; or double-upgraded observational studies | High | Further research is very unlikely to change our confidence in the estimate of effect |
| Downgraded randomized trials; or single upgraded observational studies | Moderate | Further research may change the estimate (and is likely to have an important influence on our confidence in the estimate of effect) |
| Double-downgraded randomized trials; or observational studies | Low | Further research is likely to change the estimate (and is very likely to have an important influence on our confidence in the estimate of effect) |
| Triple-downgraded randomized trials; or single downgraded observational studies; or case series/case reports | Very low | Any estimate of effect is very uncertain |