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Phenylalanine

A PKU screening test measures the amount of a protein called phenylalanine (Phe) in a sample of a newborn's blood. Phe is in all foods that contain protein such as milk, meats, and nuts. It's also in an artificial sweetener called aspartame. If a newborn has high levels of Phe in their blood, it could mean that they have phenylketonuria (PKU).

A PKU test is used to see if a newborn has high blood levels of Phe in their blood. Though PKU is rare, all newborns in the United States are tested for it.

Source: MedlinePlus, U.S. National Library of Medicine

Normal range

12 published ranges, each from a named source
18 y+
45–106 nmol/mL
19 y+
35–85 nmol/mL
Ranges from ARUP Laboratories Test Directory, Mayo Clinic Laboratories (Pediatric Test Catalog).

All source ranges (12)
SourceSexAgeRange
ARUP Laboratories Test Directory All all ages 6–20 umol/L
ARUP Laboratories Test Directory All all ages <5 umol/L
ARUP Laboratories Test Directory All ≤ 30 d 30–95 umol/L
ARUP Laboratories Test Directory All 30 d – 11 mo 30–90 umol/L
ARUP Laboratories Test Directory All 1 y+ 30–82 umol/L
Mayo Clinic Laboratories (Pediatric Test Catalog) All ≤ 1 mo 38–137 nmol/mL
Mayo Clinic Laboratories (Pediatric Test Catalog) All ≤ 2 y 36–105 nmol/mL
Mayo Clinic Laboratories (Pediatric Test Catalog) All 30 d – 2 y 31–75 nmol/mL
Mayo Clinic Laboratories (Pediatric Test Catalog) All 2 y – 18 y 26–91 nmol/mL
Mayo Clinic Laboratories (Pediatric Test Catalog) All 2 y – 17 y 38–116 nmol/mL
Mayo Clinic Laboratories (Pediatric Test Catalog) All 18 y+ 45–106 nmol/mL
Mayo Clinic Laboratories (Pediatric Test Catalog) All 19 y+ 35–85 nmol/mL

What an abnormal result can be associated with

A high result
Hyperphenylalaninemia
A low result
Hypophenylalaninemia
Associations from LOINC2HPO (Human Phenotype Ontology). This is reference information, not a diagnosis: only a clinician can interpret your result in context.
details
Sample
Serum or plasma · LOINC
Part of
Amino acids panel
Listed under
Phenylketonuria
Code
LOINC 14875-9 · umol/L
Also known as
Phe, PPA
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