Drop a PDF here or click to browse — text extracted automatically
▸ View Oxford CEBM Levels of Evidence Reference Table
| Grade | Level | Type of Study |
|---|---|---|
| A | 1a | SR (with homogeneity) of RCTs and of prospective cohort studies |
| 1b | Individual RCT with narrow CI; prospective cohort study with good follow-up | |
| 1c | All-or-none studies; all-or-none case series | |
| B | 2a | SR (with homogeneity) of cohort studies |
| 2b | Individual cohort study (including low-quality RCT, e.g. <80% follow-up) | |
| 2c | Outcomes research; ecological studies | |
| 3a | SR of case-control studies; SR of 3b and better studies | |
| 3b | Individual case-control study; nonconsecutive cohort study | |
| C | 4 | Case series / case report; poor-quality cohort studies |
| D | 5 | Expert opinion, bench research, animal studies, editorials |