Summary & Overview
CPT 84432: Thyroglobulin Tumor Marker Assay, Serum or Plasma
CPT code 84432 represents a laboratory assay for thyroglobulin, a thyroid-specific protein commonly used as a tumor marker to monitor patients after treatment for differentiated thyroid cancer. Nationally, thyroglobulin testing is clinically important for detecting residual or recurrent disease and guiding surveillance strategies, making the code relevant for payers, laboratories, and clinicians involved in endocrine and oncology care.
Key payers discussed include Aetna, Blue Cross Blue Shield, Cigna Health, UnitedHealthcare, and Medicare. The publication reviews coverage and billing considerations across major commercial and federal payers and highlights common modifiers used with laboratory services. It provides clinical context on when thyroglobulin testing is typically ordered and where the service is performed.
Readers will find a concise overview of the clinical utility of the test, the service type (clinical laboratory tumor marker assay), typical site of service (clinical or hospital laboratory), and what to expect in payer handling and billing workflows. The piece also outlines benchmarking and policy-relevant topics that affect reimbursement and utilization management for thyroglobulin testing. Data not provided in the source material are noted as unavailable.
Billing Code Overview
CPT code 84432 reports a laboratory analysis for thyroglobulin (Tg), a protein produced exclusively by thyroid follicular cells and used as a tumor marker in patients with thyroid disease. The test is typically performed on serum or plasma and is used to measure circulating thyroglobulin concentrations, often as part of monitoring for residual or recurrent differentiated thyroid cancer following thyroidectomy or other therapy.
Service type: Clinical laboratory test — tumor marker assay
Typical site of service: Clinical laboratory or hospital laboratory
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Clinical & Coding Specifications
Clinical Context
A typical patient is a 52-year-old woman with a history of differentiated thyroid carcinoma who presents for postoperative surveillance. The clinician orders a serum thyroglobulin test (84432) to monitor for residual thyroid tissue or recurrent disease after total thyroidectomy and radioactive iodine ablation. A phlebotomist draws a serum sample in an outpatient laboratory or hospital outpatient setting. The sample is sent to the clinical chemistry laboratory where a lab analyst performs the thyroglobulin assay; results are reported to the ordering endocrinologist or oncology team. The test is also used in conjunction with anti-thyroglobulin antibody testing and neck ultrasound when indicated. Typical sites of service include hospital outpatient laboratories, independent clinical laboratories, and physician office laboratories performing venipuncture and specimen analysis.
Coding Specifications
| Modifier | Description | When to Use |
|---|---|---|
26 | Professional component | When only the professional interpretation component is billed separately (rare for immunoassays). |
TC | Technical component |