Thiopurine S-Methyltransferase (TPMT) Genotype : 37742

TPMTG or 37742

TPMT Genotype; Mercaptopurine Toxicity; Azathioprine Toxicity; TPMT Deficiency

Lavender (EDTA). Also acceptable Yellow (ACD Solution A or B), Green top (no gel) Sodium heparin.

Transport 5 mL whole blood. (Min: 3 mL) Do not freeze.

Refrigerated.

Ambient: 8 days; Refrigerated: 8 days; Frozen: Unacceptable

Lithium heparin.

Wednesday & Friday

5-6 days (From receipt at performing laboratory)

This test detects 95% of the mutations in the TPMT gene and thus not all intermediate or slow metabolizers will be identified.

This test was developed and its analytical performance characteristics have been determined by Quest Diagnostics. It has not been cleared or approved by FDA. This assay has been validated pursuant to the CLIA regulations and is used for clinical purposes.

By report.

Thiopurine S-methyltransferase (TPMT; S-adenosyl-L-methionine:thiopurine S-methyltransferase) catalyzes thiopurine S-methylation, an important metabolic pathway for antineoplastic and immunosuppressive drugs. In the US, 11% of the population show intermediate TPMT activity, and approximately 1 in 300 have TPMT deficiency. Given potentially fatal nature of hematopoietic toxicity when full doses of mercaptopurine or azathioprine are given to TPMT deficient patients, and the difficulty to measure TPMT activity accurately when patients have been given red cell transfusions, the molecular method to determine TPMT genotype permits prospective identification of patients at risk.