Funding for this research was provided by:
U.S. National Library of Medicine (T15LM011271)
Received: 8 July 2016
Accepted: 30 September 2016
First Online: 13 October 2016
Compliance with ethical standards
: Institutional Review Board approval was obtained for analysis of the data and was exempted from the consent requirement due to the de-identified nature of the data. The authors do not know of any ethical issues to declare.
: The authors declare that they have no conflicts of interest.