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Thiopurine S-Methyltransferase (TPMT) Genotype : 37742
Test CodeTPMTG or 37742
Alias/See Also
TPMT Genotype; Mercaptopurine Toxicity; Azathioprine Toxicity; TPMT Deficiency
CPT Codes
81335
Instructions
Lavender (EDTA). Also acceptable Yellow (ACD Solution A or B), Green top (no gel) Sodium heparin.
Transport Container
Transport 5 mL whole blood. (Min: 3 mL) Do not freeze.
Transport Temperature
Refrigerated.
Specimen Stability
Ambient: 8 days; Refrigerated: 8 days; Frozen: Unacceptable
Reject Criteria (Eg, hemolysis? Lipemia? Thaw/Other?)
Lithium heparin.
Methodology
Polymerase Chain Reaction (PCR)
Setup Schedule
Wednesday & Friday
Report Available
5-6 days (From receipt at performing laboratory)
Limitations
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.
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.
Reference Range
By report.
Clinical Significance
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.
Performing Laboratory
Quest Diagnostics