1. Regional Paediatric Cardiology Service, Department of Paediatrics, University Teaching Hospital Ryhov, Jönköping, Sweden
2. Children’s Heart Centre, Scania University Hospital and Lund University, Lund, Sweden
3. Clinical Laboratory Science, University Teaching Hospital Ryhov, Jönköping, Sweden
4. Department of Chemistry, University of Turku, Turku, Finland
5. Research and Development Division, PerkinElmer, Turku, Finland