Type of bias | Zhu et al.21 | Schunmann and Glasier19 | Nobili et al.17 | Langston et al.22 | Carneiro Gomes Ferreira et al.18 | Bender and Griersson20 |
---|---|---|---|---|---|---|
Random sequence generation (selection bias) | + | – | – | + | + | + |
Allocation concealment (selection bias) | ? | – | – | + | ? | ? |
Blinding of participants and study personnel (performance bias) | – | – | ? | + | ? | ? |
Blinding of outcome assessment (detection bias) | – | ? | – | – | ? | ? |
Incomplete outcome data (attrition bias) | + | + | + | + | ? | – |
Selective reporting (reporting bias) | ? | ? | ? | + | ? | ? |
Other bias | + | + | – | ? | – | – |
Key: +, low risk of bias; −, high risk of bias; ?, unclear risk of bias.