TPMT and NUDT15

Casandra

Casandra Test Code AR72888Version 1 (DRAFT)

Performing Lab

Lab ARUP LaboratoriesLab Test ID 3001535CPT Codes 81306, 81335

Also known as: TPMT2

Clinical Use

Order Test

Use

This genotyping test assesses genetic risk for severe myelosuppression with standard dosing of thiopurine drugs in individuals for whom thiopurine therapy is being considered or who have had an adverse reaction to this therapy. Variants in TPMT and NUDT15 affect the inactivation of thiopurine drugs, which is used for autoimmune diseases, inflammatory bowel disease, acute lymphoblastic leukemia, and to prevent rejection after solid organ transplant. Accumulation of cytotoxic metabolites from these variants leads to increased risk of drug-related toxicity.

Special Instructions

Counseling and informed consent are recommended for genetic testing, especially for New York state clients where it is required. The test may be performed irrespective of whether thiopurine therapy is currently being administered.

Limitations

Only targeted TPMT and NUDT15 variants will be detected by this test. The complex TPMT*3A allele contains the variants found in the *3B and *3C alleles; therefore, the test cannot distinguish the *3A/negative genotype (intermediate enzyme activity) from the rare *3B/*3C genotype (no or low enzyme activity). Genotyping may reflect donor status in patients who have received allogeneic stem cell or bone marrow transplants within 2 weeks of specimen collection. Diagnostic errors can occur due to rare sequence variations, and genotyping does not replace therapeutic drug monitoring and clinical observation. Analytical sensitivity and specificity are greater than 99 percent.

Test Details

New York Approved