Authors’ contributions
Yue Liu and Xiaohong Guan contributed to the determination of study topic and design of the study. Yue Liu and Yun Zhang mainly conducted the article search, extracted the data, performed the assessment of methodological quality of enrolled studies and pooled the results. Yue Liu contributed to the original manuscript writing. Xiaohong Guan was in charge of oversight and leadership responsibility for the research activity planning and execution. All authors approved the final version of the manuscript to be published.