Preferred Sample Type

Biopterin (Blood)
2 x 8mm blood spots OR 0.5mL (minimum volume 100uL) plasma

Specimen Transport

Contact laboratory before sending. First Class post

Sample Processing in Laboratory

Transport sample frozen to Ref Lab

Sample Preparation

Dried blood spots (2 x 8mm) preferred. If plasma, centrifuge sample and freeze plasma on separation.

Turnaround Time

2-4 weeks

Sample 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



Supply serum phenylalanine concentration with request. Contact reference Lab before sending sample.

Reference Range

Provided by reference laboratory


  • EQA Scheme?: No
  • EQA Status: No EQA Scheme available

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Protection of Personal Information – Laboratory Medicine comply with the Trust Data Protection Policy and have procedures in place to allow the Directorate and it’s employees to comply with the Data Protection Act 1998 and associated best practice and guidance.

The Trust Laboratories at Heartlands Hospital, Good Hope Hospital and Solihull Hospital were awarded UKAS (United Kingdom Accreditation Service) accreditation to the internationally recognised ISO 15189 standard in May 2015. For a list of accredited tests and other information please visit the test database
Tests not appearing on this scope are either under consideration or in the process of accreditation and so currently remain outside of our scope of accreditation. However, these tests have been validated to the same high standard as accredited tests and are performed by the same trained and competent staff.

For further information contact Louise Fallon, Quality Manager, 0121 424 1235