Funding for this research was provided by:
Excellent Team of Young Teachers Foundation of Heilongjiang Province (2018-KYYWF-0916)
Heilongjiang Provincial Health and Family Planning Commission on Scientific Research Project (2018-290, 2018-291)
Jiamusi University President Innovation and Entrepreneurship Fund Project (XZYF2018-43)
Received: 12 August 2019
Accepted: 7 January 2020
First Online: 31 January 2020
Ethics approval and consent to participate
: The study protocol was approved by the Ethics Committee of Jiamusi University Clinical Medical College for research. The committee’s reference number is 20180326. Individual informed consent was waived by the ethics committee listed above because this study used currently existing sample collected during the course of routine medical care and did not cause any additional risks to the patients.
: Not applicable.
: The authors declare that they have no competing interests.