Funding for this research was provided by:
Beijing Municipal Administration of Hospitals (DFL20151501)
Key Project of the Department of Science and Technology (D141107005214003)
Received: 26 June 2018
Accepted: 5 June 2019
First Online: 21 June 2019
Ethics approval and consent to participate
: This study was approved by the Ethics Committee of Beijing Chest Hospital, affiliated to Capital Medical University. The Institutional Review Board approved the waiver of informed consent for a retrospective study because this study would bring no more than minimal risk to the subjects.
: Not applicable.
: The authors declare that they have no competing interests.