1. Department of Pediatrics, University Medical Center Groningen, University of Groningen, Groningen, the Netherlands
2. Department of Internal Medicine, University Medical Center Groningen, University of Groningen, Groningen, the Netherlands
3. Division of Clinical Chemistry, Department of Laboratory Medicine, Karolinska Institutet, Stockholm, Sweden
4. Clinical Chemistry, Karolinska University Laboratory, Karolinska University Hospital, Stockholm, Sweden