Quality of evidence | Study design | Lower if * | Higher if * |
---|---|---|---|
High | Randomised trial | Study quality: -1 Serious limitations -2 Very serious limitations -1 Important inconsistency Directness: -1 Some uncertainty -2 Major uncertainty -1 Sparse data -1 High probability of Reporting bias | Strong association: +1 Strong, no plausible confounders, consistent and direct evidence** +2 Very strong, no major threats to validity and direct evidence*** +1 Evidence of a Dose response gradient +1 All plausible confounders would have reduced the effect |
Moderate | |||
Low | Observational study | ||
Very low |