Turnaround times
The quoted turnaround time is from sample receipt in the laboratory, to results authorisation in the Laboratory Information Management system. The times do not include transport of specimen to the laboratory or the administrative process to print and post/email reports. Service users must allow for transport and reporting time when ordering tests.
Clinical background:
Phenylketonuria (PKU) is one of the most common inherited metabolic disorders with an average incidence across the UK of approximately 1 in 10,000 births, although there is geographical variance.
PKU is an autosomal recessively inherited disorder of amino acid metabolism caused by a deficiency of the enzyme phenylalanine hydroxylase. This enzyme is required to metabolise phenylalanine to tyrosine, and a deficiency results in the accumulation of phenylalanine and associated metabolites in blood and tissues.
The infant brain is sensitive to high phenylalanine levels and if left untreated, patients with PKU develop severe mental retardation, microcephaly and a proportion of patients develop epilepsy. Children with PKU requiring treatment are treated with a phenylalanine restricted diet to reduce the flux through the affected metabolic pathway thereby preventing the accumulation of toxic metabolites.
Dietary therapy utilises a phenylalanine-free synthetic amino acid mixture as a substitute for natural protein and requires careful management to ensure appropriate vitamins and trace elements together with small amounts of natural protein are provided. Blood phenylalanine levels must be closely monitored and diet adjusted so that blood phenylalanine levels stay within accepted ranges to enable normal growth and intellectual function.
Minimum volume paediatric:
One blood spot
Minimum volume adult:
One blood spot
Special requirements:
Used only for monitoring known PKU patients.
Quality assurance:
NEQAS
Reference ranges:
No ranges quoted. The assay is used only for monitoring of known PKU patients.
Other info:
User Information Sheet – information for adult patients with PKU who carry out home monitoring of their PKU. This information sheet provides details of the different methods that can be used for monitoring and how to take the samples. Information on where to obtain supplies and detailed information regarding packaging and mailing is included.