Table 2.
Risk of bias assessment of studies included
| Study ID | 1 | 2 | 3 | 4 | 5 | 6 | 7 | Risk of bias of studies |
|---|---|---|---|---|---|---|---|---|
| Abdulwahab5 | L | L | L | L | L | L | L | L |
| Schleder16 | L | L | L | L | L | L | L | L |
| Mason17 | L | L | L | L | L | L | L | L |
| Lawary18 | L | L | L | L | L | L | L | L |
| Berberich19 | L | L | L | L | L | L | L | L |
| Forloine20 | L | L | L | L | L | L | L | L |
| McLean21 | L | L | L | L | L | L | L | L |
| Hinkley22 | L | L | L | L | L | L | L | L |
| Replogle23 | L | L | L | L | L | L | L | L |
| Burns24 | L | L | L | L | L | L | L | L |
| Bradley25 | U | U | L | U | L | L | U | M |
| Cohen26 | U | U | U | U | L | L | U | M |
| Kramp27 | L | L | L | L | L | L | L | L |
| Nusstein28 | L | L | L | L | L | L | L | L |
| Replogle29 | L | L | L | L | L | L | L | L |
| Shi30 | L | L | L | L | L | L | L | L |
| Chen31 | L | L | L | L | L | L | L | L |
| Wu32 | L | U | U | U | U | U | U | M |
| Li33 | U | U | U | U | U | U | U | M |
| Dong34 | L | U | U | U | U | L | U | M |
| Liu35 | U | U | U | U | U | U | U | M |
| Xing36 | U | U | U | U | U | U | U | M |
| Luo37 | U | U | U | U | U | U | U | M |
| Ge38 | U | U | U | U | U | U | U | M |
| Xuan39 | U | U | U | U | U | U | U | M |
| He40 | U | U | U | U | U | U | U | M |
| Zhou41 | L | U | U | U | U | U | U | M |
| Jin42 | U | U | U | U | U | U | U | M |
L, means low risk of bias; U, means unknown risk of bias; M, means moderate risk of bias.