Article History
Received: 24 April 2018
Revised: 3 June 2018
Accepted: 15 June 2018
First Online: 10 July 2018
Compliance with ethical standards
:
: The scientific guarantor of this publication is Xue-Mei Wang.
: The authors of this manuscript declare no relationships with any companies whose products or services may be related to the subject matter of the article.
: One of the authors (Yun-Fei Cai) has significant statistical expertise.
: Written informed consent was not required for this study because of the nature of our study, which was a systemic review and meta-analysis.
: Institutional review board approval was not required because of the nature of our study, which was a systemic review and meta-analysis.
: All the study subjects have been previously reported in literature because this is a systemic review and meta-analysis.
: • Systemic review• Meta-analysis performed at one institution