Table 1.
Grading system for quality of evidence
| Grade of evidence | Sampling | Design | Information |
|---|---|---|---|
| A1 | Representative | Longitudinal prospective | Clinical and autopsy |
| A2 | Non-representative | Longitudinal prospective | Clinical and autopsy |
| B1 | Representative | Longitudinal prospective | Clinical only |
| B2 | Non-representative | Longitudinal prospective | Clinical only |
| C1 | Representative | Cross-sectional | Clinical and autopsy |
| C2 | Non-representative | Cross-sectional | Clinical and autopsy |
| D1 | Representative | Cross-sectional | Clinical only |
| D2 | Non representative | Cross-sectional | Clinical only |