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HelpTest Code FATPMM Thiopurine Methyltransferase Activity Profile, Erythrocytes
Additional Codes
| Mayo | TPMT3 |
| Epic ID | LAB2735 |
Special Instructions
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: Lavender top (EDTA)
Acceptable: Green top (sodium or lithium heparin), dark blue top (metal free sodium heparin), or non-centrifuged plasma gel tubes
Specimen Volume: 5 mL
Collection Instructions: Send whole blood specimen. Do not centrifuge.
Specimen Minimum Volume
3 mL
Specimen Stability Information
| Specimen Type | Temperature | Time |
|---|---|---|
| Whole blood | Refrigerated (preferred) | 6 days |
| Ambient | 6 days |
Transport refrigerated.
Reject Due To
| Gross hemolysis | Reject |
Performing Laboratory
Mayo Clinic Laboratories in Rochester
Method Name
Liquid Chromatography Tandem Mass Spectrometry (LC-MS/MS)
Testing Algorithm
For more information see:
-Ulcerative Colitis and Crohn Disease Therapeutic Drug Monitoring Algorithm
-TPMT Testing in the Treatment of Inflammatory Bowel Disease Algorithm
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
Day(s) Performed
Monday, Wednesday, Friday
Report Available
4 to 7 daysReference Values
6-Methylmercaptopurine (normal): 3.00-6.66 nmol/mL/h
6-Methylmercaptopurine riboside (normal): 5.04-9.57 nmol/mL/h
6-Methylthioguanine riboside (normal): 2.70-5.84 nmol/mL/h
CPT Code Information
84433