Mayo Clinic Laboratories’ TPNUQ genotyping assay is an innovative evaluation that examines two genes with known associations to thiopurine metabolism. In this test specific episode of the "Answers From the Lab" podcast, Ann Moyer, M.D., Ph.D., explains how TPNUQ, when used in combination with enzyme activity testing, provides insight on a patient’s risk for thiopurine toxicity.

“It’s really important to do this testing before (patients) are actually prescribed that first dose of their medication,” Dr. Moyer says. “It has been included in the FDA label to test for both TPMT and NUDT15 prior to starting a thiopurine because we know that these drugs can be very toxic to those individuals that have reduced metabolism.”

TPNUQ’s ability to detect for variations in two genes enables insights for more patients, says Dr. Moyer. “If a patient happens to have an NUDT15 variant and not a TPMT variant, we used to just miss them. So, especially since we're in the United States and we've got a lot of population diversity, I think it's really important to include both TPMT and NUDT15 together, because that's the best way to predict which patients are at risk of toxicity.”

Listen to learn more about how TPNUQ can help clarify patients’ ability to metabolize thiopurines and optimize outcomes.

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Podcast episode in video format

Testing

TPNUQ   | Thiopurine Methyltransferase (TPMT) and Nudix Hydrolase (NUDT15) Genotyping, Varies

Useful information

• Predicting potential for toxicity to thiopurine drugs (6-mercaptopurine, 6-thioguanine, and azathioprine)

Specimen requirements

Multiple genotype tests can be performed on a single specimen after a single extraction. See Multiple Genotype Test List for a list of tests that can be ordered together.

Submit only 1 of the following specimens:

Specimen Type: Whole blood

Container/Tube: Lavender top (EDTA)

Specimen Volume: 3 mL

Collection Instructions:

1. Invert several times to mix blood.
2. Send whole blood specimen in original tube. Do not aliquot.

Specimen Stability Information: Ambient (preferred) 9 days/Refrigerated 30 days

Specimen Type: Saliva

Patient Preparation: Patient should not eat, drink, smoke, or chew gum 30 minutes prior to collection.

Supplies: Saliva Swab Collection Kit (T786)

Specimen Volume: 1 Swab

Collection Instructions: Collect and send specimen per kit instructions.

Specimen Stability Information: Ambient 30 days

Specimen Type: Extracted DNA

Container/Tube: 2-mL screw top tube

Specimen Volume: 100 mcL

Collection Instructions:

1. The preferred volume is 100 mcL at a concentration of 50 ng/mcL.
2. Provide concentration of DNA and volume on tube.

Specimen Stability Information: Frozen (preferred)/Ambient/Refrigerated

Performance information

• Analytic time: 1 to 4 days
• Day(s) and time(s) performed: Monday through Friday
• Specimen Retention Time: Whole blood/Saliva: 2 weeks; Extracted DNA: 2 months

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