Funding for this research was provided by:
Helse Nord RHF
Received: 25 January 2018
Accepted: 16 March 2018
First Online: 3 May 2018
Ethics approval and consent to participate
: Approval from medical research ethical committees and data protection authorities was granted according to the regulations of each participating country; in Norway this was from the Regional Committee for Medical and Health Research Ethics NORD, number 53/96. Oral informed assent was obtained from all children. Written informed consent was obtained from parents of children aged < 16 years and from the children if aged ≥ 16 years of age.
: Not applicable.
: The authors declare that they have no competing interests.
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