Funding for this research was provided by:
Received: 13 February 2019
Accepted: 17 May 2019
First Online: 20 June 2019
Ethics approval and consent to participate
: This study protocol was approved by the Medical Ethics Committee of the Leiden University Medical Center (P14.095) and informed consent was signed by both parents and/or legal guardians of all subjects.
: The obtained data during this study was anonymised for research purposes. No personal data is included in this study.
: The authors declare that they have no competing interests.