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 | Quasi-randomised trial | ||
Low | Observational study | ||
Very low | Any other evidence |