Extended tetrahydrobiopterin loading test in the diagnosis of cofactor-responsive phenylketonuria: a pilot study

Détails

ID Serval
serval:BIB_90F5B038493B
Type
Article: article d'un périodique ou d'un magazine.
Collection
Publications
Titre
Extended tetrahydrobiopterin loading test in the diagnosis of cofactor-responsive phenylketonuria: a pilot study
Périodique
Molecular Genetics and Metabolism
Auteur(s)
Fiege  B., Bonafe  L., Ballhausen  D., Baumgartner  M., Thony  B., Meili  D., Fiori  L., Giovannini  M., Blau  N.
ISSN
1096-7192
Statut éditorial
Publié
Date de publication
12/2005
Peer-reviewed
Oui
Volume
86 Suppl 1
Pages
S91-5
Notes
Journal Article
Research Support, Non-U.S. Gov't --- Old month value: Dec
Résumé
Patients with tetrahydrobiopterin (BH4)-responsive phenylalanine hydroxylase (PAH) deficiency may benefit from BH4 therapy instead or in addition to the low-phenylalanine diet. Different loading test protocols are currently used to detect these patients. As a consequence, data on the rate of BH4-responsiveness within patients with mild phenylketonuria (PKU) and/or more severe phenotypes show high variation and a more sensitive and standardised BH4 loading test protocol needs to be defined. We modified the current standard BH4 loading test (20 mg/kg) to a second administration of 20 mg/kg after 24 h and extended blood sampling to 48 h in 24 patients with PAH deficiency. Using this extended loading test (2 x 20 mg BH4/kg), the rate of BH4-responsiveness was calculated at 8, 24, and 48 h after BH4 administration. We defined three groups of patients: "rapid responders" in 10/24 patients (4 mild HPA, 2 mild PKU, 2 moderate PKU, and 2 classic PKU), "moderate responders" in 4/24 patients (4 classic PKU), and "slow responder" in 4/24 patients (4 mild PKU). Six out of 24 patients (1 mild HPA, 1 moderate PKU, and 4 classic PKU) were found to be "non-responder." Individual phenylalanine profiles show variations in responsiveness at different time points and sampling over 48 h was more informative than over 24h in patients with mild and moderate PKU compared to mild HPA. Analysis of BH4 loading tests in 209 patients with the standard BH4 loading test protocol confirms only minor importance of the 24 h response: the rate of responsiveness to BH4 after 24 h was shown to be equal to or even lower than after 8h among most phenotypes. However, extension of the BH4 loading test to 48 h and repeated BH4 administration seems to be useful to detect BH4-responsiveness in more severe phenotypes and allows detecting "slow responders" who may benefit from BH4 therapy.
Mots-clé
Biopterin/administration & dosage/*analogs & derivatives/diagnostic use Humans Male Mutation Phenylalanine/*blood Phenylalanine Hydroxylase/deficiency/genetics Phenylketonurias/blood/*diagnosis/drug therapy Sensitivity and Specificity
Pubmed
Web of science
Création de la notice
21/01/2008 13:50
Dernière modification de la notice
03/03/2018 19:27
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