Phenylalanine, Quantitative, Plasma

CPT: 82131
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Special Instructions

Blood spots on filter paper are not an acceptable specimen type. This test is not to be used for newborn screening.

Expected Turnaround Time

3 - 5 days

Related Information

Specimen Requirements


Plasma, frozen


0.5 mL

Minimum Volume

0.25 mL


Preferred: Frozen plasma from green-top (sodium heparin) tube. Acceptable: Frozen plasma from green-top (lithium heparin) tube, frozen plasma from lavender-top (EDTA) tube or frozen plasma from PPT™. Frozen serum from serum separator tube (SST) or frozen serum from red-top tube will not be rejected. Note: Plasma reference ranges will be applied to all specimen types.


Separate plasma from cells. Transfer specimen to plastic transport tube before freezing. To avoid delays in turnaround time when requesting multiple tests on frozen samples, please submit separate frozen specimens for each test requested.

Storage Instructions

Centrifuge, remove plasma from cells, and freeze immediately.

Stability Requirements



Room temperature





14 days

Causes for Rejection

Gross hemolysis; room temperature or thawed specimens; specimens collected in yellow-top (ACD) tubes

Test Details


This test was developed, and its performance characteristics determined, by LabCorp. It has not been cleared or approved by the US Food and Drug Administration (FDA).


Liquid chromatography/tandem mass spectrometry (LC/MS-MS)

Reference Interval

See Plasma Amino Acid Reference Intervals in the Test Resources pages online.


Bremer HJ, Duran M, Kamerling JP, et al. Disturbances of Amino Acid Metabolism: Clinical Chemistry and Diagnosis. Baltimore, Md: Urban and Schwarzenberg; 1981.


Order Code Order Code Name Order Loinc Result Code Result Code Name UofM Result LOINC
700205 Phenylalanine, Qn, P 14875-9 700033 Phenylalanine umol/L 14875-9
700205 Phenylalanine, Qn, P 14875-9 700168 Phenylalanine(mg/dL) mg/dL 2765-6
700205 Phenylalanine, Qn, P 14875-9 700065 Methodology 49549-9
700205 Phenylalanine, Qn, P 14875-9 700471 Disclaimer: N/A

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