Summary & Overview
CPT 0404U: DiviTum®TKa Serum Thymidine Kinase Activity Assay
Headline: New PLA Code 0404U Captures DiviTum®TKa Serum Immunoassay to Monitor Proliferation in Metastatic HR+ Breast Cancer
Lead: CPT code 0404U designates a proprietary serum immunoassay, DiviTum®TKa (Biovica Inc.), that quantifies thymidine kinase activity to monitor cell proliferation and assess treatment effectiveness for female patients with metastatic hormone receptor–positive breast cancer. The code formalizes billing for a single-manufacturer laboratory test with algorithmic result interpretation.
Why it matters: PLA status makes 0404U specific to one commercial test, which affects coding clarity, payer policy development, and claims processing for precision monitoring in oncology. National payers are increasingly evaluating such assays for clinical utility in guiding systemic therapy decisions and monitoring response.
Payers covered: Analysis considers major national payers including Aetna, Blue Cross Blue Shield, Cigna Health, UnitedHealthcare, and Medicare.
What readers will learn: The publication summarizes the clinical scope of CPT code 0404U, describes the service type and typical sites of service, and provides benchmarks and policy context relevant to proprietary oncology monitoring assays. It outlines expected documentation elements, payer coverage considerations, and where to find procedural clarity for billing a PLA test tied to a single manufacturer. Regulatory and reimbursement trend discussion focuses on how PLA coding influences payer review pathways and laboratory adoption nationally.
Billing Code Overview
CPT code 0404U is a Proprietary Laboratory Analyses (PLA) code for the DiviTum®TKa assay by Biovica Inc. The test is a serum-based immunoassay that measures thymidine kinase activity (TKa) to monitor cell proliferation in female patients with metastatic hormone receptor–positive breast cancer. Results are produced using an algorithmic analysis that can assist in evaluating treatment effectiveness.
Service type: Laboratory — Proprietary molecular/biochemical assay
Typical site of service: Clinical laboratory or hospital outpatient laboratory using a serum specimen
Data not available in the input for associated taxonomies, ICD-10 diagnoses, related codes, and service line.
Clinical & Coding Specifications
Clinical Context
A 62-year-old woman with metastatic hormone receptor–positive (estrogen and/or progesterone receptor positive), HER2-negative breast cancer is undergoing systemic endocrine therapy with or without targeted agents. The treating oncologist orders the DiviTum® TKa test (0404U) using a serum specimen to measure thymidine kinase activity as a biomarker of tumor cell proliferation. Blood draw for the serum assay is typically performed at the outpatient oncology clinic or an ambulatory phlebotomy site on the day of a routine clinic visit or at a laboratory collection center. The specimen is sent to the manufacturer-designated laboratory or reference lab performing the proprietary immunoassay. Results are received electronically and used by the oncologist to monitor treatment response and inform discussions about ongoing systemic therapy effectiveness during follow-up visits. Typical workflow steps: 1) order placed in the electronic medical record for 0404U; 2) outpatient phlebotomy collects a serum specimen following standard venipuncture; 3) specimen is labeled, processed, and shipped per lab instructions to the performing laboratory; 4) laboratory performs the immunoassay and algorithmic analysis; 5) result report is returned to the ordering clinician and documented in the medical record; 6) clinician reviews results with the patient to assess proliferation trends and treatment effectiveness.
Coding Specifications
| Modifier | Description | When to Use |
|---|---|---|
26 | Professional component | Use when billing only the professional interpretation component if separated from the technical laboratory component. |
TC | Technical component | Use when billing only the technical component (laboratory processing) if separated. |
QX | Ordering physician not rendering service (modifier for CLIA compliance) | Use when the individual who ordered the test is not the performing laboratory and Medicare/contracting rules require attestation of non-involvement (commonly for specimen procurement relationships). |
QY | Ordering physician is also performing provider (appropriate use attestation) | Use when the ordering provider is also the performing provider under applicable laboratory regulations. |
AS | Regional anesthesia (not applicable) | Not typically used for serum laboratory tests; included in the modifier list but generally not applicable. |
52 | Reduced services | Use if the laboratory test was partially performed or shortened from the full protocol and payer guidance permits reduced service reporting. |
59* | Distinct procedural service (not in provided list) | Data not available in the input. |
78 | Return to the operating/procedure room for a related procedure during global period | Not typically applicable for this outpatient lab test; use only if an associated invasive procedure required immediate return. |
53 | Discontinued procedure | Use if specimen collection or testing was discontinued prior to completion and payer allows reporting of discontinued services. |
62 | Two surgeons (shared billing) | Not applicable to laboratory testing but listed in input; use only if surgical shared billing occurs in associated care. |
| Taxonomy Code | Specialty | Notes |
|---|---|---|
| 207RG0100X | Medical Oncology | Medical oncologists commonly order and interpret 0404U results for systemic therapy monitoring. |
| 207RH0000X | Hematology-Oncology | Hematology-oncology specialists manage complex cancer cases and may order tumor proliferation assays. |
| 364S00000X | Clinical Laboratory | Laboratory directors and clinical laboratory specialists oversee specimen handling, testing, and reporting for proprietary assays. |
| 207Q00000X | Gynecologic Oncology | Gynecologic oncologists may be involved when breast cancer care overlaps in multidisciplinary settings. |
*Note: Modifier 59 was not included in the provided modifier list; it is marked here as not available in the input.
Related Diagnoses
| ICD-10 Code | Description | Clinical Relevance |
|---|---|---|
C50.911 | Malignant neoplasm of unspecified site of right female breast | Represents metastatic or primary breast cancer where proliferation monitoring with 0404U may be indicated. |
C50.912 | Malignant neoplasm of unspecified site of left female breast | As above for left-sided breast malignancy where serial thymidine kinase activity can monitor treatment response. |
C50.919 | Malignant neoplasm of unspecified site of unspecified female breast | Used when laterality is not specified in documentation for breast cancer being monitored. |
C79.81 | Secondary malignant neoplasm of breast | Indicates metastatic disease involving the breast or other sites; proliferation biomarker testing may be used in broader metastatic monitoring. |
Z85.3 | Personal history of malignant neoplasm of breast | Relevant in surveillance contexts where increasing proliferation markers may prompt clinical evaluation for recurrence or progression. |
Related CPT Codes
| CPT Code | Description | Relationship to This Procedure |
|---|---|---|
0404U | DiviTum® TKa (thymidine kinase activity) assay, serum, immunoassay with algorithmic analysis (Proprietary Laboratory Analyses) | Primary code for the proprietary serum thymidine kinase activity test used to monitor cell proliferation in metastatic hormone-positive breast cancer. |
36415 | Collection of venous blood by venipuncture | Performed at the outpatient clinic or phlebotomy center to obtain the serum specimen required for 0404U testing. |
80053 | Comprehensive metabolic panel (CMP) | Common laboratory panel ordered alongside tumor monitoring tests to assess organ function before or during systemic therapy. |
85027 | Complete blood count (CBC) with automated differential | Frequently ordered in oncology follow-up to monitor hematologic status concurrent with biomarker testing. |
85025 | Complete blood count (CBC) without differential | Alternative CBC code used based on clinical need when differential is not required. |
81479 | Unlisted molecular pathology procedure | Occasionally used for additional non-standardized molecular analyses when no specific CPT exists; may be performed in parallel with proprietary assays depending on clinical need. |