Declaration of interests
The authors have no conflicts of interests to disclose.
Contribution to authorship
Lingying Wu and Kun Song: Study design; Yana Ma, Ning Li and Hualei Bu: Wrote and edited the article; Chengjuan Jin: Assisted in editing the article; Yongwen Huang, Chengjuan Jin, Hao Wen, Shuai Feng, Hui Zhang, Beihua Kong: Provision of resources. All authors had full access to all the data in the study and had final responsibility for the decision to submit for publication.