Table 2 Quality assessment of the included studies
| Random-sequence generation | Allocation concealment | Blinding of participants and personnel | Blinding of outcome assessment | Incomplete outcome data | Selective reporting | Other bias | |
|---|---|---|---|---|---|---|---|
| Putensen et al. [13] | ? | ? | – | ? | + | ? | – |
| Varpula et al. [10] | ? | + | – | ? | + | ? | ? |
| Li et al. [12] | ? | ? | – | ? | + | ? | ? |
| Zhou et al. [11] | + | + | – | ? | + | + | + |
| Hirshberg et al. [16] | + | + | – | ? | + | + | + |