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Synonyms
- TPMT Genetic Testing
Special Instructions
Test orders for TPMT Genotyping must include an attestation that the provider has the patient's informed consent for genetic testing. See sample physician office consent form (Informed Consent for TPMT Genetic Testing) in Related Documents.
Expected Turnaround Time
7 - 15 days
Turnaround time is defined as the usual number of days from the date of pickup of a specimen for testing to when the result is released to the ordering provider. In some cases, additional time should be allowed for additional confirmatory or additional reflex tests. Testing schedules may vary.
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7 - 15 days |
Related Documents
For more information, please view the literature below.
Specimen Requirements
Specimen
Whole blood or LabCorp buccal swab (buccal swab collection kit)
Volume
3 mL
Minimum Volume
1 mL (Note: This volume does not allow for repeat testing).
Container
Lavender-top (EDTA) tube, yellow-top (ACD) tube, green-top (heparin) tube, or LabCorp buccal swab (from kit)
Storage Instructions
Room temperature
Stability Requirements
Temperature | Period |
|---|---|
Room temperature | 28 days |
Refrigerated | 28 days |
Causes for Rejection
Frozen sample; hemolysis
Test Details
Use
Detects the most common genotypes in approximately 95% of patients. Use is recommended prior to initiating thiopurine therapy.1
Limitations
This assay will not detect approximately 5% of known deficiency mutations, and only the exons containing mutations in question are tested; polymorphisms or some sequence variants might affect efficiency of the PCR or mini-sequencing assays; assay does not distinguish between TPMT*1/3A heterozygote and the very rare compound heterozygote TPMT*3B/3C.
This test was developed, and its performance characteristics determined, by LabCorp. It has not been cleared or approved by the US Food and Drug Administration (FDA).
Methodology
Polymerase chain reaction (PCR) and multiplex mini-sequencing
Footnotes
1. Relling MV, Gardner EE, Sandborn WJ, et al. Clinical Pharmacogenetics Implementation Consortium guidelines for thiopurine methyltransferase genotype and thiopurine dosing. Clin Pharmacol Ther. 2011 Mar; 89(3):387-391. 21270794
References
Lennard L. Implementation of TPMT testing. Br J Clin Pharmacol. 2014 Apr; 77(4):704-714. 23962279
LOINC® Map
| Order Code | Order Code Name | Order Loinc | Result Code | Result Code Name | UofM | Result LOINC |
|---|---|---|---|---|---|---|
| 504142 | TPMT Genetic Test | 41048-0 | 504144 | TPMT Genotype | 41048-0 | |
| 504142 | TPMT Genetic Test | 41048-0 | 504145 | TPMT Interpretation | 62365-2 | |
| 504142 | TPMT Genetic Test | 41048-0 | 504146 | TPMT Comment | 77202-0 | |
| 504142 | TPMT Genetic Test | 41048-0 | 504143 | Background | 36922-3 |
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