Summary & Overview

CPT 85597: Phospholipid-Dependent Coagulation Assay

CPT code 85597 represents a laboratory coagulation assay that measures clotting time after adding phospholipids derived from platelet membranes to a patient blood specimen. This phospholipid-dependent test is clinically relevant for evaluating coagulation pathways and platelet function where phospholipid availability influences clot formation. Nationally, such specialized coagulation assays inform diagnosis and management of bleeding and thrombotic disorders and are performed primarily in clinical or hospital laboratories.

Key payers considered in this analysis include Aetna, Blue Cross Blue Shield, Cigna Health, UnitedHealthcare, and Medicare. Readers will find a concise overview of the code’s clinical purpose and service setting, summaries of payer coverage patterns and common modifiers, and contextual benchmarks for utilization where available. The publication also outlines clinical context for ordering the assay and typical laboratory workflow implications. Data not available in the input will be noted where relevant. The content is intended to support stakeholders — including laboratory medical directors, billing staff, and policy analysts — in understanding where CPT code 85597 fits into coagulation testing portfolios and payer coverage landscapes.

AetnaBlue Cross Blue ShieldCigna HealthUnitedHealthcareMedicare85597CPTcoagulationlaboratoryphospholipid-dependent assayplatelet membranediagnostic testingclinical laboratory

Billing Code Overview

CPT code 85597 describes a laboratory assay in which a lab analyst evaluates clotting time after adding phospholipids from platelet membranes to a patient blood specimen. This test assesses the effect of platelet-derived phospholipids on coagulation and is used in diagnostic evaluation of clotting function.

Service type: Laboratory diagnostic test — coagulation/phospholipid-dependent assay

Typical site of service: Clinical laboratory or hospital laboratory

Data not available in the input.

Clinical & Coding Specifications

Clinical Context

A patient presents for laboratory evaluation of a suspected coagulation disorder after a history of unexplained bleeding and/or a prolongation of routine coagulation assays. Typical patients include adults or children with abnormal bleeding, recurrent thrombosis on anticoagulation, suspected antiphospholipid syndrome, or evaluation of lupus anticoagulant when screening tests (e.g., prolonged activated partial thromboplastin time) are abnormal. The clinical workflow begins with a clinician order for coagulation studies; a phlebotomy technician draws a citrated plasma specimen and the specimen is labeled and sent to the laboratory. The laboratory technologist performs screening tests (PT/INR, aPTT). If an abnormal aPTT or clinical suspicion of an antiphospholipid antibody exists, the lab performs the platelet neutralization procedure to assess phospholipid-dependent clotting by adding platelet-derived phospholipids to the patient specimen and measuring correction of clotting time. Results are reported to the ordering clinician with interpretation (e.g., correction suggests a phospholipid-dependent inhibitor) and incorporated into clinical decision-making for anticoagulation management, further serologic testing, or hematology referral. Typical site of service is an outpatient or hospital clinical laboratory with testing performed by credentialed medical laboratory scientists.

Coding Specifications

Modifier	Description	When to Use
`26`	Professional component	Use when billing only the professional interpretation component provided by a physician for the laboratory test result.
`TC`	Technical component	Use when billing only the technical component (laboratory performance, equipment, and supplies) of the test.
`90`	Reference (outside) laboratory	Use when the test is performed by an external reference laboratory and the ordering facility bills for the service.
`91`	Repeat clinical diagnostic laboratory test	Use when a subsequent repeat of the same test is performed on the same day to obtain a separate result.
`59`	Distinct procedural service	Use when the test is billed in conjunction with other services and is separate and independent from other procedures performed the same day.
`52`	Reduced services	Use when the test is partially reduced or not performed to full extent.
`53`	Discontinued procedure	Use when the test was started but discontinued for patient safety or other clinical reasons.
`22`	Increased procedural services	Use when the laboratory test required substantially greater resources or time than typical and documentation supports unusual effort.
`90`	Reference (duplicate listing for emphasis)	Use as above when an outside lab performs the assay.
`91`	Repeat (duplicate listing removed)	Use as above when repeating the test.

Taxonomy Code	Specialty	Notes
208000000X	Clinical Pathology	Pathologists oversee laboratory testing and result interpretation.
360100000X	Laboratory Director	Medical directors or laboratory physicians responsible for quality and oversight.
173P00000X	Hematology	Hematologists order and interpret coagulation and antiphospholipid testing.
207Q00000X	Internal Medicine	Hospitalists and internists commonly order coagulation panels and follow-up testing.
207R00000X	Family Medicine	Primary care clinicians who initiate evaluation for bleeding or clotting disorders.

Related Diagnoses

ICD-10 Code	Description	Clinical Relevance
`D68.5`	Primary thrombophilia	Associated with evaluations for abnormal clotting; platelet neutralization can assist in identifying phospholipid-dependent inhibitors contributing to thrombosis.
`D68.9`	Coagulation defect, unspecified	Indicates unexplained coagulation abnormalities prompting phospholipid-dependent testing.
`D68.61`	Antiphospholipid syndrome	Directly related; the platelet neutralization procedure helps assess phospholipid-dependent anticoagulant effects consistent with antiphospholipid antibodies.
`R79.1`	Abnormal coagulation profile	Used when routine coagulation tests are abnormal and further phospholipid-dependent assays are indicated.
`R58`	Hemorrhage, not elsewhere classified	Presentations with bleeding may prompt coagulation testing including this procedure to identify inhibitors or platelet-related causes.

Related CPT Codes

CPT Code	Description	Relationship to This Procedure
`85730`	Thrombin time (TT); quantitative	Performed when evaluating fibrinogen function or presence of thrombin inhibitors, often ordered alongside phospholipid-dependent assays.
`85610`	Prothrombin time, partial thromboplastin time and test for mixing studies	Routine screening coagulation assays that frequently precede or accompany platelet neutralization/phospholipid assays.
`85613`	Thromboplastin time, partial thromboplastin time, and mixing study interpretation	Used when mixing studies are required to distinguish factor deficiencies from inhibitors; related to interpretation of correction with phospholipids.
`86141`	Antiphospholipid (anticardiolipin) antibody, IgG	Serologic antiphospholipid testing often performed in the diagnostic workup when phospholipid-dependent clotting abnormalities are suspected.
`86336`	Platelet antibody, platelet-associated IgG (direct)	May be ordered in evaluation of platelet-related causes of abnormal clotting and to correlate with platelet-neutralization findings.