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Risk of bias summary.
| Denny 201328 | Toft 20144 | Hidalgo‑Tenorio 201731 | Levin 201034 | Wilkin 201839 | |
|---|---|---|---|---|---|
| Random sequence generation (selection bias) |  |
 |
 |
 |
 |
| Allocation concealment (selection bias) |  |
 |
 |
 |
 |
| Blinding of participants and personnel (performance bias) |  |
 |
 |
 |
 |
| Blinding of outcome assessment (detection bias) |  |
 |
 |
 |
 |
| Incomplete outcome data (attrition bias) |  |
 |
 |
 |
 |
| Selective reporting bias (reporting bias) |  |
 |
 |
 |
 |
| Other bias |  |
 |
 |
 |
 |
low risk; 
high risk; 
unclear risk
