[1] Royal Manchester Childrens Hosp, Willink Biochem Genet Unit, Manchester M27 4HA, Lancs, England
[2] Sheffield Childrens Hosp, Dept Neonatal Screening, Sheffield, S Yorkshire, England
[3] Massachusetts Gen Hosp, Amino Acid Disorders Lab, Boston, MA 02114 USA
[4] AMC Amsterdam, Lab Genet Metab Dis, Amsterdam, Netherlands
[5] AMC Amsterdam, Dept Child Neurol, Amsterdam, Netherlands
[6] UMC Utrecht, Dept Metab & Endocrine Dis, Utrecht, Netherlands