Summary & Overview
CPT 0034U: TPMT and NUDT15 Genotyping (Mayo Clinic)
CPT code 0034U is a Proprietary Laboratory Analyses (PLA) code that identifies the Mayo Clinic’s TPMT and NUDT15 genotyping assay. The test detects genetic variants in TPMT and NUDT15 that affect thiopurine metabolism and can influence dosing and safety of thiopurine medications used in leukemia, autoimmune diseases, and transplant care. Because this is a PLA code tied to a single proprietary test, it is important for payers, laboratories, and clinicians to recognize the specific test and its clinical indications.
Key payers covered in this analysis include Aetna, Blue Cross Blue Shield, Cigna Health, UnitedHealthcare, and Medicare. Readers will find a national overview of the code’s clinical context, descriptions of expected service settings, and what to expect in payer coverage considerations for proprietary genetic tests. The publication summarizes benchmarking topics, relevant policy and coding updates, and clinical implications of TPMT and NUDT15 genotyping for thiopurine therapy management. Data not available in the input will be noted where applicable.
Billing Code Overview
CPT code 0034U is a Proprietary Laboratory Analyses (PLA) code for Thiopurine Methyltransferase (TPMT) and Nudix Hydrolase 15 (NUDT15) Genotyping performed by Mayo Clinic. The test analyzes the TPMT and NUDT15 genes to detect common variants that affect thiopurine metabolism, which influences how patients process medications used for leukemia, autoimmune diseases, and prevention of organ transplant rejection.
Service Type: Genetic/genomic laboratory test (proprietary genotyping assay)
Typical Site of Service: Clinical laboratory or hospital laboratory; specimen collection may occur in outpatient clinics or physician offices
Clinical & Coding Specifications
Clinical Context
A 10-year-old child with newly diagnosed acute lymphoblastic leukemia (ALL) is scheduled to begin maintenance therapy that includes thiopurine agents such as mercaptopurine. The oncology team orders pre-treatment pharmacogenetic testing to identify functional variants in thiopurine methyltransferase (TPMT) and nudix hydrolase 15 (NUDT15) that predict thiopurine metabolism and toxicity risk. A peripheral blood sample is collected in the outpatient infusion clinic or pediatric clinic and sent to Mayo Clinic’s laboratory for the proprietary genotyping assay reported with CPT code 0034U. The lab performs targeted genotyping for common TPMT and NUDT15 variants, generates a report indicating metabolizer status (e.g., normal, intermediate, poor), and the result is reviewed by the treating oncologist to inform thiopurine dosing and monitoring strategy. Typical sites of service include outpatient hospital laboratories, independent reference laboratories, pediatric oncology clinics, and inpatient hospital settings when pre-treatment testing is required prior to thiopurine administration. The service type is a proprietary laboratory analysis (PLA) molecular/genetic test specific to Mayo Clinic’s TPMT and NUDT15 genotyping assay.
Coding Specifications
| Modifier | Description | When to Use |
|---|---|---|
90 | Reference (outside) laboratory | Use when Mayo Clinic performs the genotyping as a reference lab and another lab/clinic bills the technical component. |