TPMT Genetics

Clinical Use

Use

The TPMT Genetics test is used to genotype a patient to aid in individualizing starting doses of thiopurines. This test is crucial before initiating therapy as it provides information that can help determine effective dosing, balancing maximum efficacy with minimized toxicity. It classifies patients into one of three genotypes: homozygous normal (wild type), heterozygous, or homozygous mutant. This information helps reduce time to response, allows physicians to tailor dosing more accurately, and identifies patients where thiopurine therapy should be avoided to reduce the risk of leukopenia.

Special Instructions

This test is performed exclusively at Prometheus Laboratories, a high complexity CLIA certified and CAP accredited clinical laboratory in San Diego, California. It has been analytically and clinically validated under CLIA guidelines but is not cleared or approved by the US FDA. Prior consent is required for genetic testing according to state regulations.

Limitations

This laboratory-developed test, not being FDA-cleared or approved, means it may not have undergone the same level of regulatory scrutiny as other approved tests. While it has been internally validated, its status as a laboratory-developed test could affect its coverage by insurance providers. Furthermore, the test only assesses the TPMT gene for known variants involved in thiopurine metabolism, not detecting all potential genetic variations in other genes that might impact drug metabolism.

Test Details