Table 1.
Criteria for assigning levels of evidence to publications of interest
| Level of evidence | Type of evidence |
|---|---|
| 1+ | High‐qualitya randomized controlled trials (RCTs) |
| Meta‐analysis or systematic review of trials with level 1+ | |
| 1 | RCTs that fail to meet level 1+ evidence |
| Meta‐analysis or systematic review of trials with level 1 | |
| 2 | Prospective cohort studies, or meta‐analysis or systematic review of them |
| Pre‐specified sub‐analyses of RCTs | |
| 3 | Non‐randomized controlled trials |
| Self‐controlled (before‐after) studies | |
| Retrospective cohort studies | |
| Case–control studies, or meta‐analysis or systematic review of them | |
| Post‐hoc sub‐analyses of RCTs | |
| 4 | Cross‐sectional studies |
| Case‐series |
a
A high‐quality RCT was defined as a trial that was appropriately designed and conducted with a large sample size and a clearly specified randomization scheme, involving double masking and a high follow‐up rate.