Source of body of evidence | Initial rating of quality | Factors that may decrease the quality | Factors that may increase the quality | Final quality of a body of evidence * |
---|---|---|---|---|
Randomised trials | High | 1. Risk of bias | 1. Large effect | High |
2. Inconsistency | 2. Dose–response | (⊕⊕⊕⊕ or A) | ||
3. Indirectness | 3. All plausible residual confounding would reduce the demonstrated effect or would suggest a spurious effect if no effect was observed | Moderate | ||
4. Imprecision | (⊕⊕⊕◯ or B) | |||
Observational studies | Low | 5. Publication bias | Low | |
(⊕⊕◯◯ or C) | ||||
Very low | ||||
(⊕◯◯◯ or D) |