1. ; Department of Clinical Biochemistry; Academic Medical Centre, University of Amsterdam; Amsterdam The Netherlands
2. ; Department of Pediatrics; Johns Hopkins University School of Medicine, Kennedy Krieger Research Institute; Baltimore Maryland USA
3. ; Department of Neurology; Johns Hopkins University School of Medicine, Kennedy Krieger Research Institute; Baltimore Maryland USA
4. ; Department of Clinical Chemistry, Metabolic Unit; Free University Hospital; Amsterdam The Netherlands
5. ; Department of Pediatrics; Academic Medical Centre, University of Amsterdam; Amsterdam The Netherlands