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HelpTest Code TPMT3 Thiopurine Methyltransferase Activity Profile, Erythrocytes
Secondary ID
65188Special Instructions
Method Name
Liquid Chromatography-Tandem Mass Spectrometry (LC-MS/MS)
Specimen Type
Whole bloodSpecimen 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.