CPT® Code 81346

TYMS (thymidylate synthetase) (eg, 5-fluorouracil/5-FU drug metabolism), gene analysis, common variant(s) (eg, tandem repeat variant)

The CPT® Code 81346 pertains to the gene analysis of thymidylate synthetase (TYMS), which is crucial for understanding the metabolism of the chemotherapeutic agent 5-fluorouracil (5-FU). The TYMS gene encodes the enzyme thymidylate synthase, which plays a significant role in the synthesis of DNA by converting deoxyuridine monophosphate (dUMP) to deoxythymidine monophosphate (dTMP), a precursor necessary for DNA replication and repair. This gene is located on the short (p) arm of chromosome 18 at position 11.32. The analysis focuses on identifying common variants, particularly tandem repeat variants, which are known to influence how individuals metabolize 5-FU. Understanding these variants is essential for predicting the risk of toxicity associated with 5-FU treatment, as certain mutations can lead to adverse effects such as mucositis, neutropenia, nausea, diarrhea, and neurological changes. The test is particularly relevant for patients undergoing chemotherapy, as it helps in assessing both the potential for drug toxicity and the responsiveness of tumors to 5-FU. The analysis is performed on a blood sample, which is collected through a separate procedure, and utilizes advanced techniques such as polymerase chain reaction (PCR) and single nucleotide extensions combined with fragment analysis to detect the specific genetic variants associated with TYMS.