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.
What is TPMT test results?
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.
How long does TPMT results take?
Test results will be ready in 2 business days.
How is TPMT measured?
The TPMT enzyme activity is measured in red blood cells so if you have recently received a transfusion of blood the results of this test may be inaccurate.
What do high TPMT levels 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.
What is the blood test for azathioprine?
Before prescribing azathioprine, your doctor will order a blood test for an enzyme called TPMT, also known as thiopurine methyltransferase (thio-pew-reen meth-ile-trans-fe-raise). Enzymes are proteins in your body that can help to break down certain substances or chemicals.
What is TPMT polymorphism?
Abstract. Thiopurine methyltransferase (TPMT) catalyses the S-methylation of thiopurines, including 6-mercaptopurine and 6-thioguanine. TPMT activity exhibits genetic polymorphism, with about 1/300 inheriting TPMT deficiency as an autosomal recessive trait.
Why is it important to check TPMT levels before commencing azathioprine?
A further 10% of people have lower than normal TPMT and are likelier than people with normal activity to develop bone marrow suppression. Testing TPMT activity before starting azathioprine can identify people who are TPMT deficient and who should not receive the drug.