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Thiopurine Methyltransferase (TPMT), Enzyme Activity, Erythrocytes
- TPMT Biochemical Assay, Myelotoxicity
Determination of TPMT levels that may be associated with toxicity of anticancer and anti-inflammatory drugs
For patients having an intrinsic low level of TPMT, recent RBC transfusion can variably increase their assayed enzymatic activity depending on the amount and circulating half-life of the transfused red blood cells.
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).
Enzymatic endpoint/liquid chromatography/tandem mass spectrometry (LC/MS-MS).
• Normal: 15.1−26.4 units/mL RBC
• Heterozygous for low TPMT variant: 6.3−15.0 units/mL RBC
• Homozygous for low TPMT variant: <6.3 units/mL RBC
8 mL adults; 5 mL pediatric
Green-top (sodium heparin) tube or lavender-top (EDTA) tube
Causes for Rejection
Frozen specimen; gross hemolysis
For New York state patients: Test orders for TPMT Enzyme Activity must include an attestation that the provider has the patient's informed consent for genetic testing. See sample physician office consent form (Informed Consent for TPMT Enzyme Activity Test) in Related Documents.
|Order Code||Order Code Name||Order Loinc||Result Code||Result Code Name||UofM||Result LOINC|
|510750||Thiopurine Methyltransferase||510751||TPMT Activity||Units/mL RBC||21563-2|