Thiopurine S-Methyltransferase (TPMT) Genotype

Test Code

37742

CPT Code(s)

81335

CPT Code is subject to a Medicare Limited Coverage Policy and may require a signed ABN when ordering.

Test Code

37742

CPT Code(s)

81335

CPT Code is subject to a Medicare Limited Coverage Policy and may require a signed ABN when ordering.

Not offered in Quest Diagnostics Nichols Institute (IFD) – San Juan Capistrano. Please provide SERVICE AREA INFORMATION to find available tests you can order.

In-home collection is not available in your area through Quest Mobile.

Clinical Significance

Thiopurine S-Methyltransferase (TPMT) Genotype - 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.

Test Resources

Clinical Focus

Inflammatory Bowel Disease: Laboratory Support for Diagnosis and Management

Test Details

Methodology

Polymerase Chain Reaction (PCR)

Assay Category

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(s)

See Laboratory Report

Alternative Name(s)

Azathioprine Toxicity,Mercaptopurine Toxicity,TPMT Deficiency

LOINC® Codes, Performing Laboratory

Service Area must be determined

Methodology

Polymerase Chain Reaction (PCR)

Assay Category

Reference Range(s)

See Laboratory Report

Alternative Name(s)

Azathioprine Toxicity,Mercaptopurine Toxicity,TPMT Deficiency

LOINC® Codes, Performing Laboratory

Service Area must be determined

Preferred Specimen(s)

5 mL whole blood collected in an EDTA (lavender-top) tube

Alternative Specimen(s)

Whole blood collected in a sodium heparin (green-top), or ACD-A (yellow-top) tube

Minimum Volume

3 mL

Collection Instructions

Whole blood: Normal phlebotomy procedure. Specimen stability is crucial. Store and ship room temperature immediately. Do not freeze.

Transport Container

EDTA (lavender-top) tube

Transport Temperature

Room temperature

Specimen Stability

Room temperature: 8 days
Refrigerated: 8 days
Frozen: Unacceptable

Setup Schedule

Service Area must be determined

Preferred Specimen(s)

5 mL whole blood collected in an EDTA (lavender-top) tube

Alternative Specimen(s)

Whole blood collected in a sodium heparin (green-top), or ACD-A (yellow-top) tube

Minimum Volume

3 mL

Collection Instructions

Whole blood: Normal phlebotomy procedure. Specimen stability is crucial. Store and ship room temperature immediately. Do not freeze.

Transport Container

EDTA (lavender-top) tube

Transport Temperature

Room temperature

Specimen Stability

Room temperature: 8 days
Refrigerated: 8 days
Frozen: Unacceptable

Setup Schedule

Service Area must be determined

Not offered in Quest Diagnostics Nichols Institute (IFD) – San Juan Capistrano. Please provide SERVICE AREA INFORMATION to find available tests you can order.

In-home collection is not available in your area through Quest Mobile.

Test Details

Clinical Significance

Test Resources

Reference ranges are provided as general guidance only. To interpret test results use the reference range in the laboratory report.

The CPT codes provided are based on AMA guidance and are for informational purposes only. CPT coding is the sole responsibility of the billing party. Please direct any questions regarding coding to the payer being billed.

This material contains content from LOINC® (http://loinc.org). The LOINC Table, LOINC Table Core are copyright © 1995-2019, Regenstrief Institute, Inc. and the Logical Observation Identifiers Names and Codes (LOINC) Committee and is available at no cost under the license at http://loinc.org/license.

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