The study protocol has been approved by the Ethics Committee of the Turku University Hospital in 11/2006 and will follow the rules of the current revision of the Declaration of Helsinki and the directives for clinical research by European Union (HE 20/2004). Patients or guardian won't get any financial benefits from the study. Children will be covered by the insurance (potilasvakuutus). This is an academic project and researchers have no conflicts of interests. Patient data will be confidential and won't be shared outside research group without coding. All deviations from the original protocol will be reported to the Ethics Committee of the Turku University Hospital and to the national authorities (Lääkelaitos).