Funding for this research was provided by:
Ministerio de Economía, Industria y Competitividad, Gobierno de España (PSI2009-14415-C03-01, PSI2012-38375-C03-01)
Received: 24 December 2018
Accepted: 5 May 2019
First Online: 1 June 2019
Ethics approval and consent to participate
: The study protocol was approved by the Hospital Universitario San Carlos ethics committee. All the participants signed an informed consent.
: Not applicable.
: The authors declare that they have no competing interests.
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