Phenylalanine and tyrosine
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. P...
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.
Test Details
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Discipline:
Biochemistry
Biochemistry
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Minimum Volume Adult:
0.5 mL blood
0.5 mL blood
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Minimum Volume Paediatric:
0.2 mL blood
0.2 mL blood
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Special Requirement:
This test is normally only used for monitoring the management of known diagnosed PKU patients.
Whole blood only.This test is normally only used for monitoring the management of known diagnosed PKU patients.
Whole blood only. -
Quality Assurance:
NEQAS
NEQAS
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Reference Ranges:
Phe
Tyr
Up to 4 days
40-110
30-135
5 days to 6 months
30-130
13-200
7 months to 2 years
40-140
20-160
3 years to 10 years
20-130
30-130
11 ye...
Read MorePhe
Tyr
Up to 4 days
40-110
30-135
5 days to 6 months
30-130
13-200
7 months to 2 years
40-140
20-160
3 years to 10 years
20-130
30-130
11 years to 17 years
30-115
25-125
Adult
40-100
20-110
Units: µmol/L
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Other Info:
User Information Sheet – information for adult patients with PKU who carry out home monitoring of their PKU. This information sheet - "Instructions for taking blood samples for monitoring PKU" - pr...
Read MoreUser Information Sheet – information for adult patients with PKU who carry out home monitoring of their PKU. This information sheet - "Instructions for taking blood samples for monitoring PKU" - 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.
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Routine Contact Name:
Duty Biochemist
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Routine Telephone:
Freeman: 0191 244 8889
RVI: 0191 282 9719
Freeman: 0191 244 8889
RVI: 0191 282 9719
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Routine Email:
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Specialist Test:
Yes
Yes
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Specialist Contact Name:
Metabolic Clinical Scientist
Metabolic Clinical Scientist
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Specialist Telephone:
0191 282 9685 (Consultant Clinical Scientist)
0191 282 0334 (Metabolic Laboratory)
0191 282 9685 (Consultant Clinical Scientist)
0191 282 0334 (Metabolic Laboratory)
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Specialist Email: