Included studies | Item 1 | Item 2 | Item 3 | Item 4 | Item 5 | Item 6 | Item 7 | Item 8 | Item 9 | Item 10 | Item 11 | Total score |
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Chen 2014 [11] | N | Y | Y | Y | Y | Y | Y | Y | Y | Y | N | 9 |
Wang 2012 [12] | N | Y | Y | N | Y | Y | Y | Y | Y | Y | N | 8 |
Guo 2013 [13] | N | N | Y | N | Y | N | Y | Y | Y | Y | N | 6 |
Zhou 2012 [22] | N | N | Y | N | Y | N | Y | Y | Y | Y | N | 6 |
Dong 2011 [23] | N | Y | Y | N | Y | N | Y | Y | Y | Y | N | 7 |
Ren 2006 [24] | N | N | N | N | N | N | Y | Y | Y | Y | N | 4 |
Dai 2010 [25] | N | N | Y | Y | Y | Y | Y | Y | Y | N | N | 7 |
Du 2014 [26] | N | Y | N | Y | N | N | Y | Y | Y | Y | N | 6 |
Li 2012 [27] | N | N | N | Y | Y | N | Y | N | Y | Y | N | 5 |
Xiong 2012 [28] | N | Y | Y | Y | Y | Y | Y | Y | Y | N | Y | 9 |
Wang 2013 [29] | N | Y | Y | Y | Y | Y | Y | Y | Y | N | Y | 9 |
Wu 2013 [30] | N | Y | Y | Y | Y | Y | Y | Y | Y | N | Y | 9 |
- Y means adequate; N means inadequate. Item 1. Was an a priori design provided? Item 2. Was there duplicate study selection and data extraction? Item 3. Was a comprehensive literature search performed? Item 4. Were published and unpublished studies included irrespective of language of publication? Item 5. Was a list of studies (included and excluded) provided? Item 6. Were the characteristics of the included studies provided? Item 7. Was the scientific quality of the included studies assessed and documented? Item 8. Was the scientific quality of the included studies used appropriately in formulating conclusions? Item 9. Were the methods used to combine the findings of studies appropriate? Item 10. Was the likelihood of publication bias assessed? Item 11. Was a conflict of interest stated?