Funding for this research was provided by:
Ministry of Health & Welfare, Republic of Korea (HI14C3418)
Korean government (2016R1A5A2945889)
Received: 10 October 2018
Accepted: 15 October 2018
First Online: 22 October 2018
Compliance with ethical standards
: The authors declare that they have no conflicts of interest.
: This study adhered to the ethical tenets of the Declaration of Helsinki and was approved by the Institutional Review Board of SMC in Seoul, Korea (IRB number: 2017-06-130).
: The need for informed consent was waived because of the low risk posed by this investigation.