Table 3 The assessment risk of bias
Study | Sequence generation | Allocation concealment | Blinding of participants, personnel and outcome assessors | Incomplete outcome data | Selective outcome reporting | Other bias | Overall risk of bias |
|---|---|---|---|---|---|---|---|
Liet et al. 2006 [14] | Low | Low | Low | Low | Low | Low | Low |
Standl et al. 2008 [15] | Low | Low | Unclear | Low | Low | Low | Unclear |
Akech et al. 2010 [16] | Low | Low | Unclear | Low | Low | Low | Unclear |
Van Der Linden et al. 2013 [17] | Low | Low | Low | Low | Low | Low | Low |
Liet et al. 2003 [18] | Unclear | Unclear | Low | Low | Low | Low | Unclear |
Hanart et al. 2009 [19] | Low | Low | Low | Low | Low | Low | Low |
Akkucuk et al. 2013 [20] | Unclear | Unclear | Unclear | Low | Low | Low | Unclear |
Chong Sung et al. 2006 [21] | Unclear | Unclear | Unclear | Low | Low | Low | Unclear |
Haas et al. 2007 [22] | Unclear | Unclear | Unclear | Low | Low | Low | Unclear |
Wills et al. 2005 [23] | Low | Low | Low | Low | Low | Low | Low |
Sahoo et al. 2007 [24] | Unclear | Unclear | Unclear | Low | Low | Low | Unclear |
Osthaus et al. 2009 [25] | Low | Unclear | Unclear | Low | Low | Low | Unclear |
Witt et al. 2008 [26] | Unclear | Unclear | Low | Low | Low | Low | Unclear |