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    v1.0.28
    OpenPayerBilling CodesHematology and Coagulation ProceduresCPT cpt-85670-thrombin-clotting-time-test
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    CPT 85670: Thrombin-Induced Clotting Time Assay

    CPT code 85670 describes a laboratory test performed by a lab analyst to assess clot formation time after adding thrombin to a patient’s blood sample; the service is a coagulation/thrombosis diagnostic assay typically performed in a clinical laboratory or hospital laboratory setting and is used to evaluate thrombin-induced clotting function in clinical and perioperative contexts.

    For related coverage guidance, see recent payer policy updates: Epithelial Cell Cytology in Breast Cancer Risk Assessment, Chemotherapy Observation or Inpatient Hospitalization (for New Mexico Only), Antibody-Drug Conjugates.

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    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.

    Related CPT Codes

    CPT CodeDescriptionRelationship to This Procedure
    85610Prothrombin time; plasma or whole bloodCommon complementary coagulation test used with thrombin time to evaluate the extrinsic pathway and overall clotting status.
    85730Thrombin time (quantitative)Related coagulation assay; sometimes lab panels include alternate thrombin assays or nomenclature overlaps.
    85384Fibrinogen; Clauss methodMeasures fibrinogen concentration and directly correlates with thrombin time abnormalities.
    85025Blood count; automated complete CBC with automated differentialPerformed alongside coagulation testing to assess platelet count and hematologic context for bleeding.
    36415Collection of venous blood by venipunctureThe specimen collection procedure preceding the laboratory assay.

    Related Modifiers

    7 rows

    ModifierDescriptionWhen to Use
    26Modifier 26 (Professional Component) identifies and bills only the professional portion of a split service — the physician’s interpretation, report, and medical judgment — when the technical…- Use CPT Modifier -26 when you are billing only the professional component (PC) of a split‑bill eligible service—i.e., you performed the physician interpretation, medical judgment and prepared a…
    90Modifier ‑90 (Reference/Outside Laboratory) indicates that a laboratory test was performed by an entity other than the treating or reporting provider. The American Medical Association defines…- Use CPT modifier -90 when a laboratory test is performed by an outside/reference laboratory (an entity other than the treating or reporting physician or qualified professional) and the claim needs…
    91Modifier 91 — “Repeat Clinical Diagnostic Laboratory Test” — is appended when the exact same CPT laboratory test is performed more than once for the same patient on the same day because serial,…- Use modifier 91 when the exact same CPT laboratory test is performed more than once on the same patient on the same date because serial or repeated testing is medically necessary to monitor…
    52Modifier ‑52 (Reduced Services) indicates that a service or procedure was partially reduced or omitted at the provider’s discretion, allowing reporting of the basic procedure number with a qualifier…- Use modifier -52 when a physician or qualified health professional electively reduces or omits part of a procedure or service (for example, performing fewer required views or omitting a portion of…
    53Modifier 53 (Discontinued Procedure) signals that a surgical or diagnostic service was begun by the physician but terminated because of extenuating circumstances that threatened the patient’s…- Use modifier -53 when a physician/qualified healthcare professional has started a surgical or diagnostic procedure (e.g., anesthesia administered, incision or scope insertion) and then discontinues…
    59Modifier 59 indicates a distinct procedural service when two procedures that are not normally billed together are clinically and procedurally separate. The CPT definition (as reiterated by CMS)…- Use modifier -59 to report a distinct procedural service when documentation supports that the procedure reported is not normally billed together with another service on the same day because of a…
    76Modifier -76, Repeat Procedure or Service by Same Physician or Other Qualified Health Care Professional, is appended when the same provider performs an identical, medically necessary procedure or…- Use modifier -76 when the same physician or other qualified health care professional performs an identical procedure or service a second (or subsequent) time on the same date of service and the…

    Related Provider Taxonomies

    8 rows

    Taxonomy CodeSpecialtyNotes
    207RH0000XHematology (Internal Medicine) PhysicianAn internist with additional training who specializes in diseases of the blood, spleen and lymph. This specialist treats conditions such as anemia, cl…
    207L00000XAnesthesiology PhysicianAn anesthesiologist is trained to provide pain relief and maintenance, or restoration, of a stable condition during and immediately following an opera…
    2080P0207XPediatric Hematology & Oncology PhysicianA pediatrician trained in the combination of pediatrics, hematology and oncology to recognize and manage pediatric blood disorders and cancerous disea…
    2085R0202XDiagnostic Radiology PhysicianA radiologist who utilizes x-ray, radionuclides, ultrasound and electromagnetic radiation to diagnose and treat disease.
    207RT0003XTransplant Hepatology PhysicianAn internist with special knowledge and the skill required of a gastroenterologist to care for patients prior to and following hepatic transplantation…
    364SC1501XCommunity Health/Public Health Clinical Nurse SpecialistPhysician Assistants & Advanced Practice Nursing Providers · Clinical Nurse Specialist
    156FX1202XOptometric TechnicianAn optometric technician assists optometrists by performing duties, including but not limited to, basic eye testing, diagnostic tests, and assistance …
    163WA2000XAdministrator Registered NurseNursing Service Providers · Registered Nurse

    Related ICD-10-CM Codes

    27 rows

    ICD-10-CM CodeDescription
    C91.00Acute lymphoblastic leukemia not having achieved remission
    D50.0Iron deficiency anemia secondary to blood loss (chronic)
    D63.1Anemia in chronic kidney disease
    D65Disseminated intravascular coagulation [defibrination syndrome]
    D66Hereditary factor VIII deficiency
    D67Hereditary factor IX deficiency
    D68.1Hereditary factor XI deficiency
    D68.4Acquired coagulation factor deficiency
    D68.8Other specified coagulation defects
    D68.9Coagulation defect, unspecified

    Showing 1–10 of 27

    Related Payer Policy Updates

    Specialty: Hematology/Oncology1 / 3

    4 rows

    PolicyPayerEffective Date
    Epithelial Cell Cytology in Breast Cancer Risk AssessmentOscar Health2026-10-01
    Chemotherapy Observation or Inpatient Hospitalization (for New Mexico Only)UnitedHealthcare2026-08-01
    Antibody-Drug ConjugatesPremera Bluecross2026-08-01
    Umbilical Cord Blood Harvesting and Storage for Future Use (for Indiana Only)UnitedHealthcare2026-08-01

    Related Codes

    CPT-85002-BLEEDING-TIME-TEST-LABORATORY

    CPT 85002: Bleeding Time Test, Technical Component

    CPT-85004-AUTOMATED-DIFFERENTIAL-WHITE-BLOOD-CELL-COUNT

    CPT 85004: Automated White Blood Cell Differential

    CPT-85007-MANUAL-DIFFERENTIAL-WHITE-BLOOD-CELL-COUNT

    CPT 85007: Manual Differential White Blood Cell Count

    CPT-85008-BLOOD-SMEAR-MORPHOLOGIC-REVIEW-NO-DIFFERENTIAL

    CPT 85008: Microscopic Blood Smear Examination, No Differential

    CPT-85009-MANUAL-WBC-COUNT-BUFFY-COAT

    CPT 85009: Manual White Blood Cell Count Using Buffy Coat

    CPT-85013-MICROHEMATOCRIT-TEST-LABORATORY-DIAGNOSTIC

    CPT 85013: Microhematocrit Test by Tube Centrifugation

    CPT-85014-HEMATOCRIT-VOLUME-PERCENT-RED-BLOOD-CELLS

    CPT 85014: Hematocrit (Volume Percent of Red Blood Cells)

    CPT-85018-HEMOGLOBIN-ASSAY-WHOLE-BLOOD

    CPT 85018: Hemoglobin Measurement in Whole Blood

    CPT-85025-COMPLETE-BLOOD-COUNT-CBC

    CPT 85025: Complete Blood Count (CBC)

    CPT-85027-COMPLETE-BLOOD-COUNT-HGB-HCT

    CPT 85027: Complete Blood Count with Hemoglobin and Hematocrit

    Showing 1–10 of 99

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    Frequently Asked Questions

    References

    1. 1.CPT® Codes and Descriptions. AAPC. Retrieved Aug 11, 2026.Maintains the CPT code set's official descriptions and guidelines, licensed from the American Medical Association, used as the definitional source for CPT codes on this page.
    2. 2.HCPCS Quarterly Update. Centers for Medicare & Medicaid Services (CMS). Retrieved Aug 11, 2026.CMS's quarterly release of HCPCS Level II codes and short/long descriptors, the source for HCPCS code definitions and update history.
    3. 3.ICD-10-CM Full Code List. Centers for Medicare & Medicaid Services (CMS). Retrieved Aug 11, 2026.CMS's complete ICD-10-CM diagnosis code list, used to cross-reference diagnosis codes associated with this procedure or service.
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