Table 2. Assessment of study quality and risk of bias.
| First author, year | 7-item criteria |
Total | ||||||
|---|---|---|---|---|---|---|---|---|
| A | B | C | D | E | F | G | ||
| Wang YQ, 2013 | + | − | − | ? | + | + | + | 4 |
| Zhang SQ, 2012 | + | − | − | ? | + | + | + | 4 |
| Wang ZF, 2011 | + | − | − | ? | + | + | + | 4 |
| Chen SF, 2010 | + | + | + | + | + | + | + | 7 |
| Huang JL, 2010 | + | − | − | ? | + | + | + | 4 |
| Sun JH, 2008 | + | − | − | ? | + | + | + | 4 |
| Dai MX, 2002 | + | − | − | ? | + | + | + | 4 |
| He D, 2002 | + | − | ? | ? | + | + | + | 4 |
| Fan Y, 2000 | + | − | ? | ? | + | + | + | 4 |
A to G, the 7-Item criteria. A, adequate sequence generation; B, concealment of allocation; C, blinding of participants and personnel; D, blinding of out-come assessment; E, incomplete out-come data; F, selective reporting; G, other bias; +: low risk of bias, −: high risk of bias, ?: uncertain risk of bias.