Table 2.
quality assessment of included studies
| Study ID | Adequate sequence generation | Allocation concealment | Blinding | Incomplete outcome data | Free from select reporting bias | Free from other potential sources bias |
|---|---|---|---|---|---|---|
| Chambers 2010 [8] | Unclear | Unclear | Unclear | Yes | Unclear | Unclear |
| Chuwa 2006 [11] | Unclear | Yes | Unclear | Yes | Yes | Yes |
| He 2002 [18] | Yes | Yes | Unclear | Yes | Yes | Unclear |
| Heald 1997 [16] | Yes | Unclear | Unclear | Yes | Unclear | Yes |
| Kim 2012 [12] | Yes | Yes | Unclear | Yes | Yes | Yes |
| Law 2001 [17] | Yes | Yes | Unclear | Yes | Yes | Yes |
| Li 2006 [6] | Yes | Yes | Unclear | Yes | Yes | Yes |
| Li 2009 [19] | Yes | Yes | Unclear | Yes | Yes | Yes |
| Marr 2005 [9] | Unclear | Yes | Unclear | Yes | Yes | Unclear |
| Nagtegaal 2005 [5] | Yes | Yes | Unclear | Yes | Yes | Unclear |
| Wibe 2004 [15] | Yes | Unclear | Unclear | Yes | Unclear | Yes |
| Shihab 2010 [7] | Yes | Yes | Unclear | Yes | Yes | Yes |
| Campos-Lobato 2011 [10] | Yes | Yes | Unclear | Yes | Yes | Yes |