[1] Lund Univ, Skane Univ Hosp, Dept Pediat, Lund, Sweden
[2] Umea Univ, Dept Publ Hlth & Clin Med, S-90187 Umea, Sweden
[3] Norrtalje Hosp, Pediat Clin, Norrtalje, Sweden
[4] Linkoping Univ, Dept Clin & Expt Med, Fac Hlth Sci, Norrkoping, Sweden
[5] Umea Univ, Dept Clin Sci, S-90187 Umea, Sweden