Table 2.
Quality assessment of included randomized controlled trials.
| Study ID | Assessment of methodological quality of the studies | ||||||
|---|---|---|---|---|---|---|---|
| 1 | 2 | 3 | 4 | 5 | 6 | Grade of risk bias | |
| Zhang 2018 | U | U | N | Y | Y | U | B |
| Wang 2018 | U | U | N | Y | Y | U | B |
| Cui 2017 | U | U | N | Y | Y | U | B |
| Li 2017 | U | U | N | Y | Y | U | B |
| Deng 2016 | U | U | N | Y | Y | U | B |
| Zhen 2015 | U | U | N | Y | Y | U | A |
| Wang 2014 | Y | U | N | Y | Y | U | B |
| Fan 2014 | U | U | N | Y | Y | U | B |
| Li 2013 | U | U | N | Y | Y | U | B |
| Xun 2012 | U | U | N | Y | Y | U | B |
| Ma 2012 | U | U | N | Y | Y | U | B |
| Zou 2012 | U | U | N | Y | Y | U | A |
Notes: 1: randomization; 2: allocation concealment; 3: blinding; 4: complete outcome data; 5: selective reporting of outcomes; 6: other bias; Y: yes; N: no; U: unclear.