1 Department of Pediatric Hematology and Oncology, Erasmus MC-Sophia Children's Hospital, University Medical Center Rotterdam, Rotterdam, The Netherlands.
2 Central Diagnostic Laboratory - Research, University Medical Center Utrecht, Utrecht University, Utrecht, The Netherlands.
3 Van Creveldkliniek, University Medical Center Utrecht, Utrecht University, Utrecht, The Netherlands.
4 Department of Hematology, Erasmus Medical Center, University Medical Center Rotterdam, Rotterdam, The Netherlands.