PHENYLALANINE MONITORING, PLASMA

Code
000.0000
Name
PHENYLALANINE MONITORING, PLASMA
Category
None
Department
Send-Out
Start Date
Expiration Date
Synonyms
PKU monitoring
CPT Codes
84030
Site
SBMF
Reference Test
44424
ATLAS Test Code

Specimen Information

Type

Green, Heparin

Volume

0.5 ml

Transport Info

Centrifuge and immediately transfer plasma to separate plastic tube
Frozen

Fasting Required?
False
Patient Instructions

Reference Range

0-11 months: 30-100 μmol/L
1 year and older: 30-80 μmol/L

Methodology

Ion Exchange Chromatography

Clinical Significance

This test is designed to monitor treatment and compliance in PKU patients.

Phenylketonuria (PKU) is an inherited disease characterized by the inability to metabolize phenylalanine, usually due to a deficiency of L-phenylalanine hydroxylase (97-99% of cases). A dihydropteridine reductase deficiency or defect in biopterin synthesis will also produce hyperphenylalaninemia. In about 50 percent of patients, there is total absence of phenylalanine hydroxylase, resulting in very high levels of phenylalanine in untreated patients. The buildup of phenylalanine in the brain causes progressive mental retardation. If infants with this disorder are immediately placed on low phenylalanine diets, damage is minimal. Since phenylalanine is also necessary for normal growth and development, it is critical to monitor its levels in PKU patients. It is critical to monitor women with PKU during pregnancy, since high levels of phenylalanine are teratogenic. A "Phenylalanine and Tyrosine" test is designed to monitor treatment and compliance in PKU patients, and is less useful for diagnosis. Many amino acids require a plasma specimen for accurate analysis, but either plasma or serum is acceptable for phenylalanine diet monitoring. The target for PKU treatment is phenylalanine at 80-300 µmol/L (2-5 mg/dL) and tyrosine in the normal range. Many amino acids require a plasma specimen for accurate analysis, but either plasma or serum is acceptable for phenylalanine diet monitoring.

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