What is a TPMT genetic test?

What is a TPMT genetic test?

TPMT genetic test (genotype)—an alternative test to TPMT enzyme activity level is a genetic test that can identify genetic variations in the TPMT gene. This genetic test identifies individual genetic differences associated with risk for thiopurine toxicity. Each person has two copies of the TPMT gene.

Where is the TPMT gene?

Thiopurine methyltransferase or thiopurine S-methyltransferase (TPMT) is an enzyme that in humans is encoded by the TPMT gene. A pseudogene for this locus is located on chromosome 18q.

How long does TPMT results take?

Test results will be ready in 2 business days.

What is the role of TPMT?

Normal Function The TPMT gene provides instructions for making an enzyme called thiopurine S-methyltransferase (TPMT). This enzyme carries out a specific chemical reaction called S-methylation of a group of molecules known as aromatic and heterocyclic sulphydryl compounds.

What causes TPMT deficiency?

TPMT deficiency results from changes in the TPMT gene. This gene provides instructions for making the TPMT enzyme, which plays a critical role in breaking down (metabolizing) thiopurine drugs. Once inside the body, these drugs are converted to toxic compounds that kill immune system cells in the bone marrow.

What do low TPMT levels mean?

Complete TPMT deficiency (TPMT <10 nmol/h/g Hb) indicates that there is an absolute intolerance to thiopurine drugs. Low activity indicates partial enzyme deficiency and therefore that the probability of azathioprine-induced bone marrow depression or nausea is HIGH.

How does the TPMT enzyme affect a azathioprine drug?

Genetic polymorphisms influence TPMT and NUDT15 activity. Several published studies indicate that patients with reduced TPMT or NUDT15 activity receiving usual doses of 6-MP or azathioprine, accumulate excessive cellular concentrations of active 6-TGNs, and are at higher risk for severe myelosuppression.

Is there a genetic test for thiopurine toxicity?

TPMT genetic test ( genotype )—an alternative test to TPMT enzyme activity level is a genetic test that can identify genetic variations in the TPMT gene. This genetic test identifies individual genetic differences associated with risk for thiopurine toxicity. Each person has two copies of the TPMT gene.

Do you need to take a TPMT test before taking thiopurine?

Test Preparation Needed? For measuring TPMT enzyme activity (TPMT phenotyping), the test must be performed prior to taking a thiopurine drug since it may affect results; for the genetic test ( TPMT genotyping), no specific test preparation is needed. Looking for Test Results?

Is there a genetic test to detect TPMT deficiency?

The genetic test usually detects the most common variants associated with TPMT deficiency. It is possible for a person to have a rare variant not detected by this test, who may subsequently experience serious side effects from treatment with a thiopurine drug. Is there anything else I should know?

Which is the best test for thiopurine phenotyping?

The American College of Gastroenterology prefers TPMT phenotyping for people who are being treated with thiopurines for inflammatory bowel disease because the phenotype test measures the level of TPMT enzyme activity. Johnson-Davis, K. (2017 February Updated).