Summary & Overview
CPT 85670: Thrombin Clotting Time Assay
CPT code 85670 identifies a laboratory coagulation assay that measures the clot formation time after thrombin addition. This test provides a direct measure of clotting kinetics and is used in diagnostic evaluation of coagulation function, perioperative assessment, and monitoring of certain coagulopathies. Nationally, accurate coding for coagulation assays affects clinical documentation, lab workflow, and payment processes across hospital and independent laboratory settings.
Key payers covered in this analysis include Aetna, Blue Cross Blue Shield, Cigna Health, UnitedHealthcare, and Medicare. Readers will find a concise explanation of the clinical purpose of the test, the typical site of service, and which payers commonly interact with claims for this code. The publication summarizes common modifiers and payer considerations, outlines benchmarking and billing context where available, and highlights clinical scenarios in which the assay is applied. Data not available in the input is noted where relevant.
This overview is designed for billing professionals, laboratory managers, and clinicians seeking a national-level briefing on coding and payer context for CPT code 85670 without state-specific detail.
Billing Code Overview
CPT code 85670 describes a laboratory procedure in which a lab analyst measures the time to clot formation after adding thrombin to patient blood. This test evaluates clotting kinetics using thrombin as the activator and is typically performed by clinical laboratory personnel in a hospital or independent laboratory setting.
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Service type: Laboratory coagulation test
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Typical site of service: Hospital laboratory or independent clinical laboratory
Clinical & Coding Specifications
Clinical Context
A typical patient is an adult or pediatric inpatient or outpatient who requires assessment of clotting function related to thrombin-mediated pathways. Common scenarios include evaluation of suspected coagulopathies after cardiac surgery, monitoring of patients receiving fibrinogen replacement or topical thrombin products, assessment of hemostasis in trauma or perioperative bleeding, or investigation of suspected dysfibrinogenemia. The clinical workflow: a phlebotomist draws a citrated whole blood sample and the specimen is labeled and delivered to the clinical laboratory. A medical laboratory scientist or hematology technologist prepares platelet-poor plasma (if required), performs the thrombin time assay using standardized thrombin reagent, records time to clot formation, and documents results in the laboratory information system. Results are reviewed by a pathologist or clinical laboratory director when abnormal before release to the ordering clinician, who correlates the TT result with prothrombin time, activated partial thromboplastin time, fibrinogen level, and clinical bleeding history to guide management such as administration of cryoprecipitate, fibrinogen concentrate, or further hematology consultation.
Coding Specifications
| Modifier | Description | When to Use |
|---|---|---|
26 | Professional component | Use when billing only the professional component (interpretation) separate from the technical lab processing. |