1. Department of Pediatric Endocrinology, Wilhelmina Children's Hospital, University Medical Center Utrecht , Utrecht , The Netherlands
2. Princess Máxima Center for Pediatric Oncology , Utrecht , The Netherlands
3. Stem Cell Transplantation Unit, Princess Máxima Center for Pediatric Oncology , Utrecht , The Netherlands
4. Laboratory Clinical Chemistry and Hematology, University Medical Center Utrecht , Utrecht , The Netherlands
5. Mathematical Institute Leiden University, The Netherlands and Department of Biomedical Science, Section Medical Statistics, Leiden University Medical Centre , Leiden , The Netherlands
6. Department of Pediatric Oncology, University of Groningen, University Medical Center Groningen , Groningen , The Netherlands