Funding for this research was provided by:
Medical science research key project of Hebei province (20170402)
Received: 21 March 2019
Accepted: 7 May 2019
First Online: 24 June 2019
Ethics approval and consent to participate
: The study was approved by the Children’s hospital Hebei Province Ethics Committee (number 2017016). The legal guardian(s) or parent(s) of the children provided written informed consent for sample collection and clinical record review.
: Not applicable.
: The authors declare that they have no competing interests.
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