Summary & Overview
CPT 85302: Protein C Antigen Assay, Plasma
CPT code 85302 represents a laboratory measurement of protein C antigen in plasma. Protein C antigen testing is clinically important for evaluating inherited or acquired deficiencies of protein C and assessing thrombotic risk. As a specialized coagulation laboratory assay, this code is commonly billed when clinicians investigate unexplained thrombosis, recurrent venous thromboembolism, or when anticoagulant therapeutic decisions require clarification of protein C levels.
Key payers in this national context include Aetna, Blue Cross Blue Shield, Cigna Health, UnitedHealthcare, and Medicare. Readers will find a concise review of the clinical purpose of the assay, the typical laboratory setting for service delivery, and the payer landscape addressed in coverage and billing practice discussions. The publication summarizes typical sites of service, common billing modifiers (listed separately), and the implications of test utilization for clinical workflows and lab operations.
This overview provides benchmarks and policy-relevant context for laboratory administrators, billing professionals, and clinicians seeking to understand coding practices, national payer considerations, and the clinical role of protein C antigen testing. Data not available in the input is identified where applicable.
Billing Code Overview
CPT code 85302 describes a laboratory assay performed by a lab analyst to measure protein C antigen in a patient’s plasma. This test quantifies the amount of protein C, a vitamin K–dependent anticoagulant protein, and is used in the clinical evaluation of coagulation disorders and thrombotic risk.
Service Type: Laboratory test — protein C antigen assay
Typical Site of Service: Clinical laboratory or hospital laboratory
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Clinical & Coding Specifications
Clinical Context
A 42-year-old patient with a personal or family history of venous thromboembolism presents to hematology for evaluation of an unexplained deep vein thrombosis. The clinician orders specialized coagulation testing, including a protein C antigen assay, to assess for inherited or acquired deficiencies of natural anticoagulants. A phlebotomy procedure is performed in an outpatient laboratory or hospital draw station; plasma is separated and sent to the clinical laboratory. A laboratory technologist or clinical laboratory scientist runs the protein C antigen immunoassay and documents results in the laboratory information system. Results are reviewed by the ordering hematologist or pathologist and used alongside protein C functional assays, protein S testing, and genetic testing as indicated to determine the etiology of thrombophilia and guide management decisions such as anticoagulation duration.
Coding Specifications
| Modifier | Description | When to Use |
|---|---|---|
26 | Professional component | Use when reporting only the professional interpretation of the laboratory test if separated from the technical component. |
TC | Technical component | Use when reporting only the technical portion of the laboratory test (laboratory processing and reporting) without physician interpretation. |