Table 2 Risk of bias summary: review authors’ judgements about each risk of bias item for each included study
Study ID | 1.Bias due to confounding | 2.Bias in selection of participants into the study | 3.Bias in classification of interventions | 4.Bias due to deviations from intended interventions | 5.Bias due to missing data | 6.Bias in measurement of outcomes | 7.Bias in selection of the reported result | overall risk of bias |
|---|---|---|---|---|---|---|---|---|
Ali 2009 [19] | *** | **** | **** | **** | **** | **** | a | *** |
Xiaoping Fan 2011 | *** | **** | **** | ** | *** | **** | a | ** |
Yuanling Li 2014 [27] | *** | **** | **** | **** | **** | **** | a | *** |
Jianjun Zou 2006 [10] | ** | **** | **** | **** | **** | **** | a | *** |
Jie Luo 2012 [23] | ** | **** | **** | **** | **** | **** | a | ** |
Zhenjing Liu 2006 [11] | ** | **** | * | **** | **** | **** | a | * |
Noritoshi 1998 [8] | ** | **** | **** | **** | *** | **** | **** | ** |
Nobuhisa 2015 [28] | ** | **** | **** | **** | * | **** | a | * |
Liping Zhao 2007 [14] | ** | **** | **** | **** | **** | **** | a | ** |
Lianxue Zheng 2009 [16] | * | **** | **** | **** | **** | **** | a | * |
Ruihong Kong 2009 [17] | * | **** | **** | **** | * | **** | a | * |
Zaili Feng 2014 [26] | ** | **** | **** | **** | **** | **** | a | ** |
Xue Xu 2011 [20] | *** | **** | **** | **** | **** | **** | a | **** |
Lina Wang 2013 [24] | **** | **** | **** | **** | *** | **** | a | *** |
Fang Ding 2008 [15] | ** | **** | **** | **** | **** | **** | a | ** |
Zhaoxia Li 2009 [18] | ** | **** | *** | **** | **** | **** | a | ** |
Bo Yang 2015 [29] | **** | **** | *** | **** | **** | **** | a | *** |
Yuqian Sun 2012 [22] | ** | **** | *** | **** | **** | **** | a | ** |
Alexandra 2006 [13] | *** | **** | **** | **** | **** | **** | a | *** |
H. Bozcuk 2001 [9] | *** | **** | **** | **** | **** | **** | a | *** |
Liping Fu 2013 [25] | ** | **** | *** | **** | **** | **** | a | ** |
Xiuling Wang 2006 [12] | ** | **** | **** | ** | **** | **** | a | ** |
Ruifen Zhang 2016 [30] | ** | **** | **** | ** | **** | **** | a | ** |