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Test Code TPMT3 Thiopurine Methyltransferase Activity Profile, Erythrocytes

Important Note

Use Sunquest code "TPMTSS"

Synonym " TPMTSS"

Secondary ID

65188

Method Name

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

Specimen Type

Whole blood


Specimen Required


Patient Preparation: Thiopurine methyltransferase (TPMT) enzyme activity can be inhibited by several drugs and may contribute to falsely low results. Patients should abstain from the following drugs for at least 48 hours prior to TPMT testing: 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.

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 Special Container
Whole blood Refrigerated (preferred) 6 days
  Ambient  6 days

Reject Due To

Gross hemolysis Reject

Reference Values

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

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

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

Day(s) and Time(s) Performed

Monday, Wednesday, Friday; 8 a.m.

Performing Laboratory

Mayo Clinic Laboratories in Rochester

CPT Code Information

82657

Forms

1. New York Clients-Informed consent is required. Document on the request form or electronic order that a copy is on file. The following documents are available in Special Instructions:

-Informed Consent for Genetic Testing (T576)

-Informed Consent for Genetic Testing-Spanish (T826)

2. If not ordering electronically, complete, print, and send a Gastroenterology and Hepatology Client Test Request (T728) with the specimen.