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Article History

Received: 19 July 2017

Accepted: 28 June 2018

First Online: 5 July 2018

Ethics approval and consent to participate

: We obtained ethical approval as appropriate for each country.Germany:Ethics Commission of the Charité – University Medicine of Berlin (Germany); reference number EA2/069/13. Approval May 24th, 2013.Ethics Commission of the Universitat zu Lubeck, reference number 13–144. Approval July 22nd, 2013.Ethics Commission of the Medical Faculty of the Westfalische Wilhelms-Universitat Munster, reference number 2013–500-b-S, approval September 13th, 2013.Ethics Commission of the Ludwig-Maximilians Universitat Munich, reference number 450–13. Approval October 2nd, 2013.France.Comite de Protection des Personnes – Ile de France 1, reference number 13352. Approval November 5th, 2013 (Joint application for France Assistance Publique – Hopitaux de Paris, Le Centre Hospitalier Universitaire de Toulouse, Centre Hospitalier Universitaire de Montpellier, Université Claude Bernard Lyon 1 / Hospices Civils de Lyon).Poland.Medical University of Lodz, Komisja Bioetyki Uniwersytetu Medycznego w Lodzi, reference number RNN/242/13/KE. Approval September 30th, 2013.Komisja Bioethycnej przy intytucie ‘Pomnik-centrum Zdrowia Dziecka, Warsaw, reference number 103/KBE/2013. Approval September 30th, 2013.Sweden.Karolinska Institutet: Regionala etikprövningsnämnden I Stockholm, reference number 2013/1163–31/1. Approval October 23rd, 2013.The Netherlands.Medisch Ethische Toetsings commissie VU medisch centrum, reference number 2013.336. Approval October 11th, 2013.Radboud universitair medisch centrum Radboud University Nijmegen, reference number NL46220.029.13. Approval November 27th, 2013.UKUniversity of Birmingham: NHS National Health Research Ethics Service, NRES Committee North West – Greater Manchester East, reference number 14/NW/1123. Approval September 29th, 2014.We obtained written informed consent from all participants in all study sites, and if the participant was underage (below age 18), both the participants and their parents provided written informed consent in all sites.

: Not applicable.

: All authors declare no support from any organisation for the submitted work; no relationship with any organisations that might have an interest in the submitted work in the previous three years; no other relationships or activities that could appear to have influenced the submitted work. Therefore, the authors declare that they have no competing interests.

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