What is 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.

What does a high TPMT level mean?

High TPMT activity: > 65 U/mL – Individuals are not predicted to be at low risk for bone marrow toxicity as a consequence of standard thiopurine dosing, but may be at risk for therapeutic failure due to excessive inactivation of thiopurine drugs.

Where is TPMT gene located?

chromosome 18q.
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. Chr.

Why do we check TPMT?

A doctor may request a blood TPMT test before starting a patient on thiopurine drug treatment or if they suspect that existing side effects may be due to a deficiency of this enzyme. If a patient has no detectable TPMT activity then they are at risk of developing severe side effects to thiopurine drugs.

What is TPMT deficiency?

Thiopurine S-methyltransferase (TPMT) deficiency is a condition characterized by significantly reduced activity of an enzyme that helps the body process drugs called thiopurines. These drugs, which include 6-thioguanine, 6-mercaptopurine, and azathioprine, inhibit (suppress) the body’s immune system.

Why is it important to check TPMT levels before commencing azathioprine?

Patients with TPMT deficiency treated with standard doses of azathioprine or 6-mercaptopurine are at significantly increased risk of myelosuppression, bleeding, infection, and death associated with increased levels of cytotoxic 6-thioguanine nucleotide levels in the red blood cells.

How long does TPMT results take?

Test results will be ready in 2 business days.

How common is TPMT deficiency?

Studies suggest that less than 1 percent of individuals in the general population have TPMT deficiency. Another 11 percent have moderately reduced levels of TPMT activity that increase their risk of hematopoietic toxicity with thiopurine drug treatment.

How long does a TPMT test take?