What is the TPMT 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 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 is normal TPMT level?
Sies et al7 have established the normal range of TPMT to be 9.3–17.6 units/ml red blood cells. However, these results can have considerable inconsistencies as a result of factors such as recent blood transfusions, certain medications, alcohol, and interlaboratory variation.
How long does TPMT results take?
Test results will be ready in 2 business days.
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.
What are thiopurine drugs?
The thiopurine drugs are purine antimetabolites widely used in the treatment of acute lymphoblastic leukemia, autoimmune disorders (e.g., Crohn’s disease, rheumatoid arthritis), and organ transplant recipients. Metabolism is catalyzed by S-methyltransferase.
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.
How long can you stay on azathioprine?
If tolerated, you will probably be on azathioprine for up to 5 years. Do not stop taking your medicine unless your doctor tells you to, even if you feel well.
What does a high TPMT level mean?
Low activity indicates partial enzyme deficiency and therefore that the probability of azathioprine-induced bone marrow depression or nausea is HIGH.
When to use thiopurine methyltransferase ( TPMT ) lab test?
Thiopurine methyltransferase (TPMT) Typically, prior to thiopurine drug treatment; this is a specialized test and is not routinely ordered.
Where is the TPMT gene located in humans?
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. Thiopurine methyltransferase methylates thiopurine compounds.
Can a TPMT blood test be above average?
There are no counter-indications of a TPMT blood test being above average, although it is believed that having high levels of enzyme activity could prevent a thiopurine drug being as effective as it could be. This blood test is ordered to determine if there are variations within the TPMT gene that could contribute to low levels of enzyme activity.
What does TPMT testing Before azathioprine therapy?
It is a prodrug of mercaptopurine, a substance that is subsequently metabolised by several alternative pathways, one of which involves the enzyme thiopurine methyltransferase (TPMT). Some peop … TPMT testing before azathioprine therapy? Drug Ther Bull. 2009 Jan;47(1):9-12.doi: 10.1136/dtb
