Test Code TPMT3 Thiopurine Methyltransferase Activity Profile, Erythrocytes
Secondary ID
65188Useful 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
Special Instructions
Method Name
Liquid Chromatography Tandem Mass Spectrometry (LC-MS/MS)
Reporting Name
TPMT Activity Profile, RBCSpecimen 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 plasma gel 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
6-Methylmercaptopurine (normal): 3.00-6.66 nmol/mL/hour
6-Methylmercaptopurine riboside (normal): 5.04-9.57 nmol/mL/hour
6-Methylthioguanine riboside (normal): 2.70-5.84 nmol/mL/hour
Day(s) Performed
Monday, Wednesday, Friday
Report Available
4 to 7 daysPerforming Laboratory
Mayo Clinic Laboratories in RochesterTest Classification
This test was developed and its performance characteristics determined by Mayo Clinic in a manner consistent with CLIA requirements. It has not been cleared or approved by the US Food and Drug Administration.CPT Code Information
84433
LOINC Code Information
Test ID | Test Order Name | Order LOINC Value |
---|---|---|
TPMT3 | TPMT Activity Profile, RBC | 91139-6 |
Result ID | Test Result Name | Result LOINC Value |
---|---|---|
48038 | Interpretation | 59462-2 |
48034 | 6-Methylmercaptopurine | 91141-2 |
48035 | 6-Methylmercaptopurine riboside | 91142-0 |
48036 | 6-Methylthioguanine riboside | 91143-8 |
48037 | Reviewed By | 18771-6 |
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:
-Informed Consent for Genetic Testing (T576)
-Informed Consent for Genetic Testing-Spanish (T826)
2. If not ordering electronically, complete, print, and send Gastroenterology and Hepatology Test Request (T728) with the specimen
Testing Algorithm
For more information see Ulcerative Colitis and Crohn Disease Therapeutic Drug Monitoring Algorithm.