Summary & Overview
CPT 85675: Thrombin Clot Formation Time Assay
CPT code 85675 designates a laboratory assay that measures time to clot formation after adding different concentrations of thrombin to patient blood. The test provides detailed information about coagulation response to thrombin, supporting diagnostic evaluation of clotting disorders and monitoring in clinical contexts where thrombin-mediated coagulation is relevant. Nationally, accurate coding and coverage understanding for this specialized coagulation assay affect laboratory billing, clinical workflow, and patient access to targeted hemostasis testing.
Key payers covered in the analysis include Aetna, Blue Cross Blue Shield, Cigna Health, UnitedHealthcare, and Medicare. Readers will find an overview of clinical context for the assay, typical sites of service, and payer coverage considerations. The publication summarizes benchmark billing practices, common billing modifiers and service line placement, and relevant policy updates that influence reimbursement and documentation expectations. The content also highlights coding clarity to reduce claim denials and streamline laboratory reporting for coagulation testing. Data not available in the input is noted where applicable.
Billing Code Overview
CPT code 85675 describes a laboratory procedure in which a lab analyst measures the time to clot formation after adding varying concentrations of thrombin to a patient's blood. This test evaluates clotting dynamics in response to thrombin and is used to assess coagulation function under controlled reagent conditions.
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Service type: Laboratory diagnostic test
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Typical site of service: Clinical laboratory or hospital laboratory setting
Clinical & Coding Specifications
Clinical Context
A 55-year-old patient with unexplained bleeding and a history of anticoagulant therapy presents to an outpatient hematology laboratory for specialized coagulation testing. The treating hematologist orders a thrombin time (thrombin reagent concentration series) to evaluate the conversion of fibrinogen to fibrin and to assess for dysfibrinogenemia or the presence of direct thrombin inhibitors. Blood is drawn via venipuncture and sent to the clinical laboratory. A trained laboratory technologist prepares platelet-poor plasma and performs serial assays adding differing concentrations of thrombin to measure clot formation time. Results are reviewed by the laboratory director or hematologist for correlation with clinical history, concurrent coagulation testing (e.g., fibrinogen level, PT/INR, aPTT), and medication profile. The report informs diagnosis of thrombin inhibitor effect, congenital or acquired fibrinogen abnormality, or monitoring of certain anticoagulant therapies.
Coding Specifications
| Modifier | Description | When to Use |
|---|---|---|
26 | Professional component | Use when only the professional interpretation/reporting portion is billed separate from lab technical component. |
TC | Technical component |