Laboratory: Clinical Biochemistry  (SENDOUTS)
Test Name:
Test Code: MIS8
Clinical Information:
Description:  This test is used for assessment of patients with acute lymphoblastic leukemia (ALL) at risk of acute thiopurine toxicity and who are of indigenous and asian descent.

NUDT15 testing is used for predicting potential for toxicity to thiopurine drugs (6-mercaptopurine, 6-thioguanine and azathioprine).

This test includes genotyping of TPMT and NUDT15, both of which affect metabolism of thiopurine drugs.

Test Approval Requirements: Available to Pediatric Oncologists upon approval. Click here for F260-11-02 Biochemistry Approval for Test Referral Form
Recommendations: Clinical Pharmacogenetics Implementation Consortium Guideline for Thiopurine Dosing Based on TPMT and NUDT15 Genotypes: 2018 Update. Clinical Pharmacology and Therapeutics 2019, 105(5): 1095-1105

Collection Devices:
Specimen Required:
Whole Blood: 4.0 mL
Pediatric Whole Blood: 3.0 mL

Collection Information: 
1. Invert several times to mix blood.
2. Send whole blood specimen in original tube. Do not aliquot.
Special Processing: Do not centrifuge. Do not freeze.
Specimen Stability: 

Ambient: 9 days
Refrigerated: 30 days
Frozen: unacceptable
Whole Blood: 3.0 mL
Pediatric Whole Blood: 3.0 mL

Pediatric Volume: 3.0 mL (0.4 mL is required for testing)
Shipping & Storage: Send in original collection tube. Store and ship whole blood at room temperature (preferred) or refrigerated.
Referred Out Location: Specimen referred from HSC-MS5 to:
Mayo Clinic Laboratories
3050 Superior Dr. NW
Rochester, MN 55901
Phone: 800-533-1710
Test Name: Thiopurine Methyltransferase (TPMT) and Nudix Hydrolase (NUDT15) Genotyping, Varies
Reference Values:
An interpretive report will be provided.
Within 2 Weeks
See Also:
More Information:
Interpretation & Assay Interferences: Rare variants may be present that could lead to false-negative or false-positive results. If no TPMT variant alleles are detected by this assay the most likely genotype is that of TPMT*1/*1, although the presence of other rarer alleles cannot be excluded. In addition, if no NUDT15 variant alleles are detected by this assay, the most likely genotype is that of NUDT15*1/*1, although the presence of other rarer alleles cannot be excluded.
If genotype results obtained do not match the clinical findings, additional testing should be considered for thiopurine methyltransferase enzyme activity (TPMT Enzyme Activity (Phenotype), Erythrocytes)
A corresponding activity assay for NUDT15 is not currently available.