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    v1.0.28
    OpenPayerBilling CodesHematology and Coagulation ProceduresCPT cpt-85598-hexagonal-phase-phosphatidylethanolamine-clotting-assay
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    CPT 85598: Hexagonal‑Phase Phosphatidylethanolamine Clotting Test

    CPT code 85598 describes a laboratory assay in which a hexagonal-phase phosphatidylethanolamine reagent is added to a patient blood specimen to evaluate clotting time; this is a specialized coagulation test performed by a lab analyst as a diagnostic hematology service, typically provided in a clinical laboratory or hospital laboratory setting using venous blood specimens for assessment of clotting pathway function.

    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 with a history of unexplained venous or arterial thrombosis, recurrent pregnancy loss, or a thrombotic event while on anticoagulation who is being evaluated for antiphospholipid antibodies and a potential lupus anticoagulant. The laboratory receives a citrated plasma specimen from the outpatient hematology clinic or the hospital inpatient unit. The technologist performs coagulation screening tests (prothrombin time, activated partial thromboplastin time) and reflexes to specialized assays when a prolonged clotting time is detected. For this procedure, the lab analyst performs the hexagonal phase phosphatidylethanolamine neutralization test to assess for a lupus anticoagulant by adding the hexagonal phase reagent to the patient specimen and measuring clotting time changes. Results are reviewed by a clinical pathologist or hematologist, reported in the electronic medical record, and used by the ordering clinician to guide diagnosis of antiphospholipid syndrome and subsequent management planning, such as anticoagulation decisions or additional serologic testing.

    Related CPT Codes

    CPT CodeDescriptionRelationship to This Procedure
    85598Neutralization procedure to detect lupus anticoagulant using hexagonal phase phosphatidylethanolamine reagentThe primary specialized assay performed to evaluate for lupus anticoagulant when initial coagulation screens suggest antiphospholipid activity.
    85610Prothrombin timeCommon initial coagulation screening test; prolonged results can trigger reflex testing such as 85598.
    85730Thrombin timeMay be performed in coagulation panels to evaluate fibrinogen conversion and guide interpretation of lupus anticoagulant testing.
    85760Coagulation time; activated partial thromboplastin time (aPTT)Frequently used screening test for intrinsic pathway abnormalities and prolonged clotting that can lead to lupus anticoagulant testing.
    86147Antibody; anticardiolipin, each isotypeSerologic testing for antiphospholipid antibodies commonly ordered alongside lupus anticoagulant assays to evaluate antiphospholipid syndrome.

    Related Modifiers

    6 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…

    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…
    2080P0208XPediatric Infectious Diseases PhysicianA pediatrician trained to care for children in the diagnosis, treatment and prevention of infectious diseases. This specialist can apply specific know…
    363L00000XNurse Practitioner(1) A registered nurse provider with a graduate degree in nursing prepared for advanced practice involving independent and interdependent decision mak…
    207LC0200XCritical Care Medicine (Anesthesiology) PhysicianAn anesthesiologist, who specializes in critical care medicine diagnoses, treats and supports patients with multiple organ dysfunction. This specialis…
    2085R0203XTherapeutic Radiology PhysicianTherapeutic Radiology certificate name was changed to Radiation Oncology. Use Radiation Oncology.
    2471Q0001XQuality Management Radiologic TechnologistA radiologic technologist who specializes in quality management.
    261QM2800XMethadone ClinicAn entity, facility, or distinct part of a facility providing diagnostic, and replacement maintenance treatment services related to individuals with d…
    1835X0200XOncology PharmacistA licensed pharmacist who has demonstrated specialized knowledge and skill in developing, recommending, implementing, monitoring, and modifying pharma…

    Related ICD-10-CM Codes

    20 rows

    ICD-10-CM CodeDescription
    D68.2Hereditary deficiency of other clotting factors
    D68.4Acquired coagulation factor deficiency
    D68.9Coagulation defect, unspecified
    D69.3Immune thrombocytopenic purpura
    D69.6Thrombocytopenia, unspecified
    I80.9Phlebitis and thrombophlebitis of unspecified site
    I82.401Acute embolism and thrombosis of unspecified deep veins of right lower extremity
    I82.402Acute embolism and thrombosis of unspecified deep veins of left lower extremity
    I89.0Lymphedema, not elsewhere classified
    I97.2Postmastectomy lymphedema syndrome

    Showing 1–10 of 20

    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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