Received: 3 July 2018
Accepted: 31 August 2018
First Online: 7 September 2018
Ethics approval and consent to participate
: The present study was approved by the ethics committee each participating institutions in the Xinjiang province. Written informed consent was obtained for the main study and for eventual substudies The need for individual consent for this subset study was waived by the committee.
: Not applicable.
: The authors declare that they have no competing interests.
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