Project leader: Leif Bjarte Rolfsjord, M.D., section leader, Paediatric Department Sykehuset Innlandet HF Elverum-Hamar; Ragnhild Halvorsen, M.D. Ph.D., Voksentoppen, Paediatric Clinic, Rikshospitalet; Leiv Sandvik, Ph.D. professor, research leader statistics, Competence Centre for Clinical Research, Ullevaal University Hospital