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Test Code TPMT3 Thiopurine Methyltransferase (TPMT) Activity Profile, Erythrocytes

Additional Codes

UCL: YML
PowerChart: Thiopurine Methyltransferase Level
Epic: LAB2735 Thiopurine Methyltransferase

MA Cerner: Thiopurine Methyltransferase (TPMT), Erythrocytes

Secondary ID

65188

Useful For

Detection of individuals with low thiopurine methyltransferase (TPMT) activity who are at risk for excessive myelosuppression or severe hematopoietic toxicity when taking thiopurine drugs

 

Detection of individuals with hyperactive TPMT activity who have therapeutic resistance to thiopurine drugs and may develop hepatotoxicity if treated with these drugs

Method Name

Liquid Chromatography-Tandem Mass Spectrometry (LC-MS/MS)

Reporting Name

TPMT Activity Profile, RBC

Specimen Type

Whole blood


Specimen Required


Patient Preparation: Thiopurine methyltransferase (TPMT) enzyme activity can be inhibited by several drugs such as: naproxen (Aleve), ibuprofen (Advil, Motrin), ketoprofen (Orudis), furosemide (Lasix), sulfasalazine (Azulfidine), mesalamine (Asacol), olsalazine (Dipentum), mefenamic acid (Ponstel), trimethoprim (Proloprim), methotrexate, thiazide diuretics, and benzoic acid inhibitors. TPMT inhibitors may contribute to falsely low results: patients should abstain from these drugs for at least 48 hours prior to TPMT testing.

Container/Tube:

Preferred: EDTA

Acceptable: Green top (sodium heparin), metal free sodium heparin, lithium heparin or plasma separator tubes

Specimen Volume: 5 mL


Specimen Minimum Volume

3 mL

Specimen Stability Information

Specimen Type Temperature Time
Whole blood Refrigerated (preferred) 6 days
  Ambient  6 days

Reject Due To

Hemolysis

Mild OK; Gross reject

Lipemia

NA

Icterus

NA

Other

NA

Reference Values

3.00-6.66 nmol/mL/hr 6-Methylmercaptopurine (normal)

5.04-9.57 nmol/mL/hr 6-Methylmercaptopurine riboside (normal)

2.70-5.84 nmol/mL/hr 6-Methylthioguanine riboside (normal)

Day(s) and Time(s) Performed

Monday through Friday; 8 a.m.

Performing Laboratory

Mayo Medical Laboratories in Rochester

Test Classification

This test was developed and its performance characteristics determined by Mayo Clinic in a manner consistent with CLIA requirements. This test has not been cleared or approved by the U.S. Food and Drug Administration.

CPT Code Information

82657

LOINC Code Information

Test ID Test Order Name Order LOINC Value
TPMT3 TPMT Activity Profile, RBC In Process

 

Result ID Test Result Name Result LOINC Value
48038 Interpretation 59462-2
48034 6-Methylmercaptopurine In Process
48035 6-Methylmercaptopurine riboside In Process
48036 6-Methylthioguanine riboside In Process
48037 Reviewed By No LOINC Needed

Forms

1. New York Clients-Informed consent is required. Please document on the request form or electronic order that a copy is on file. An Informed Consent for Genetic Testing (T576) is available in Special Instructions.

2. If not ordering electronically, complete, print, and send a Gastroenterology and Hepatology Test Request Form (T728) with the specimen (http://www.mayomedicallaboratories.com/it-mmfiles/gastroenterology-and-hepatology-test-request.pdf)