Preferred Sample Type
Specimen Transport
Contact laboratory before sending. First Class postSample Processing in Laboratory
Transport sample frozen to Ref LabSample Preparation
Dried blood spots (2 x 8mm) preferred. If plasma, centrifuge sample and freeze plasma on separation.Turnaround Time
2-4 weeksSample Stability
-20 ºC. Store dried blood spots in sealed plastic bag.Biopterin (Blood)
General Information
Most babies found to have persistent hyperphenylalaninaemia (greater than 240 µmol/l) have abnormalities in the enzyme phenylalanine hydroxylase. However 1-2% (between 1 in 500,000 and 1 in 1,000,000 births) will have a defect in the metabolism of tetrahydrobiopterin (BH4) which is the essential cofactor for the three aromatic hydroxylases (phenylalanine, tyrosine and tryptophan hydroxylases).
In patients with normal tetrahydrobiopterin synthetic pathways, blood biopterin concentrations increases in proportion to the degree of hyperphenylalaninaemia. Differentiation of biopterin deficiency from normal is difficult in blood spots if the blood phenylalanine concentration is not appreciably raised, ideally > 400 µmol/l.
A plasma biopterin measurement may then be necessary to exclude a synthesis defect. Knowledge of the blood phenylalanine concentration at the time of sampling is essential for interpretation.
Patient Preparation
None
Notes
Supply serum phenylalanine concentration with request. Contact reference Lab before sending sample.
Reference Range
Provided by reference laboratory
Specifications
- EQA Scheme?: No
- EQA Status: No EQA Scheme available