CPT® Code 81346

Official Description

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

Common Language Description

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.

1. Indications

The TYMS gene analysis (CPT® Code 81346) is indicated for the following conditions:

Assessment of 5-FU Toxicity Risk This test is performed to identify individuals who may be at increased risk for toxicity when treated with 5-fluorouracil (5-FU), a common chemotherapeutic agent used in cancer treatment.
Evaluation of Tumor Responsiveness The analysis helps determine the likelihood of a tumor's responsiveness to 5-FU, guiding treatment decisions for patients undergoing chemotherapy.

2. Procedure

The procedure for conducting the TYMS gene analysis involves several key steps:

Step 1: Sample Collection A blood sample is obtained from the patient. This step is crucial as it provides the necessary biological material for genetic analysis. The blood draw is performed using standard venipuncture techniques, and the sample is collected in a suitable container for subsequent testing.
Step 2: DNA Extraction Once the blood sample is collected, the DNA is extracted from the white blood cells. This process involves lysing the cells to release the DNA, followed by purification to ensure that the DNA is suitable for analysis.
Step 3: Polymerase Chain Reaction (PCR) The extracted DNA undergoes polymerase chain reaction (PCR) to amplify the specific regions of the TYMS gene that are of interest. This step is essential for generating enough DNA material to detect the common variants accurately.
Step 4: Single Nucleotide Extensions and Fragment Analysis Following PCR, single nucleotide extensions are performed to identify specific variants within the TYMS gene. The resulting fragments are then analyzed to determine the presence of tandem repeat variants, which are critical for assessing 5-FU metabolism.

3. Post-Procedure

After the TYMS gene analysis is completed, the results are interpreted by a qualified healthcare professional. Patients may receive counseling regarding the implications of their test results, particularly in relation to their treatment with 5-FU. It is important to monitor for any signs of drug toxicity, such as mucositis, neutropenia, nausea, diarrhea, and neurological changes, especially in those identified as having variants that may affect drug metabolism. Follow-up care may include adjustments to chemotherapy regimens based on the findings of the gene analysis to optimize treatment efficacy and minimize adverse effects.

Short Descr	TYMS GENE COM VARIANTS
Medium Descr	TYMS GENE ANALYSIS COMMON VARIANTS
Long Descr	TYMS (thymidylate synthetase) (eg, 5-fluorouracil/5-FU drug metabolism), gene analysis, common variant(s) (eg, tandem repeat variant)
Status Code	Statutory Exclusion (from MPFS, may be paid under other methodologies)
Global Days	XXX - Global Concept Does Not Apply
PC/TC Indicator (26, TC)	9 - Not Applicable
Multiple Procedures (51)	9 - Concept does not apply.
Bilateral Surgery (50)	9 - Concept does not apply.
Physician Supervisions	09 - Concept does not apply.
Assistant Surgeon (80, 82)	9 - Concept does not apply.
Co-Surgeons (62)	9 - Concept does not apply.
Team Surgery (66)	9 - Concept does not apply.
Diagnostic Imaging Family	99 - Concept Does Not Apply
CLIA Waived (QW)	No
APC Status Indicator	Service Paid under Fee Schedule or Payment System other than OPPS
Type of Service (TOS)	5 - Diagnostic Laboratory
Berenson-Eggers TOS (BETOS)	none
MUE	1

90	Reference (outside) laboratory: when laboratory procedures are performed by a party other than the treating or reporting physician or other qualified health care professional, the procedure may be identified by adding modifier 90 to the usual procedure number.