Summary & Overview
CPT 84445: Thyroid Stimulating Immunoglobulin (TSI) Serum Test
CPT code 84445 represents a laboratory assay that measures thyroid stimulating immunoglobulins (TSI) in patient serum. This immunoassay supports diagnosis and monitoring of autoimmune hyperthyroidism, notably Graves disease, and is widely used across clinical laboratories and hospital settings. Accurate identification of TSI can influence clinical management decisions for patients with suspected or established autoimmune thyroid disorders, making the code clinically significant on a national scale.
Key payers included in this analysis are Aetna, Blue Cross Blue Shield, Cigna Health, UnitedHealthcare, and Medicare. Readers will find a concise overview of clinical context and laboratory service characteristics tied to this code, plus nationally relevant benchmarking and policy-oriented information where available. The publication summarizes common billing practices, typical sites of service, and the role of TSI testing in diagnostic workflows. It also outlines areas where policy updates or payer coverage criteria commonly affect use and reimbursement of this test.
This summary is intended for a national audience of clinicians, laboratory managers, and billing professionals seeking a clear understanding of what CPT code 84445 represents, why it matters clinically, and what to expect in payer coverage and administrative handling of TSI testing.
Billing Code Overview
CPT code 84445 measures thyroid stimulating immunoglobulins (TSI) in patient serum. The test is used to detect and quantify autoantibodies that stimulate the thyroid, aiding diagnosis and management of autoimmune thyroid conditions such as Graves disease.
Service type: Laboratory diagnostic test
Typical site of service: Clinical laboratory or hospital lab; specimen collected in outpatient clinic or inpatient setting
Clinical & Coding Specifications
Clinical Context
A 38-year-old female presents to an outpatient endocrinology clinic with symptoms of unexplained weight loss, palpitations, heat intolerance, tremor, and diffuse goiter on exam. The endocrinologist suspects autoimmune hyperthyroidism (Graves disease) and orders laboratory evaluation including measurement of thyroid stimulating immunoglobulins. A phlebotomy technician collects a serum sample during the visit. The sample is sent to the clinical laboratory where a laboratory analyst performs immunoassay testing for thyroid stimulating immunoglobulins (TSI, CPT 84445). Results are reported in the electronic medical record and reviewed by the endocrinologist for diagnosis confirmation and to guide therapy such as antithyroid medication, radioiodine consideration, or referral for ophthalmology if ophthalmopathy is suspected.
Coding Specifications
| Modifier | Description | When to Use |
|---|---|---|
26 | Professional component | Use when reporting only the professional component for laboratory testing when split billing of technical and professional components applies (less common for automated lab immunoassays). |
TC |