Summary & Overview

CPT 85260: Factor X (Stuart–Prower) Clotting Assay

CPT code 85260 represents a specialized laboratory coagulation assay to detect the presence of factor X (Stuart–Prower factor) in a patient’s serum. This assay is clinically important for diagnosing specific bleeding or thrombotic disorders and guiding hematology management. Nationally, accurate coding and recognition of this test affect lab billing, utilization tracking, and clinical decision support.

Key payers covered in the publication include Aetna, Blue Cross Blue Shield, Cigna Health, UnitedHealthcare, and Medicare. Readers will find an overview of the clinical context for ordering a factor X assay, typical sites of service, and operational considerations for laboratory billing. The publication summarizes common modifiers used with lab services and discusses typical payer coverage patterns and coding pitfalls where data are available.

The article provides benchmarks and policy updates relevant to laboratory coagulation testing, practical coding guidance for CPT code 85260, and interpretation considerations that influence payer decisions. Data limitations are noted where input information is incomplete. The intent is to offer a concise national briefing for billing professionals, laboratory managers, and clinical coders who handle specialized coagulation assays.

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Billing Code Overview

CPT code 85260 describes a laboratory clotting test performed by a lab analyst to detect the presence of factor X (Stuart–Prower factor) in a patient’s serum. This test is a specialized coagulation assay used to evaluate specific clotting factor activity when disorders of coagulation are suspected.

Service type: Laboratory diagnostic test (coagulation assay)

Typical site of service: Clinical laboratory or hospital laboratory

Clinical & Coding Specifications

Clinical Context

A typical patient is an adult or pediatric patient referred for laboratory coagulation testing after abnormal bleeding, unexpected perioperative bleeding, or as part of a workup for a prolonged prothrombin time (PT) or activated partial thromboplastin time (aPTT). A common scenario: a 45-year-old patient presents with new-onset easy bruising and mucosal bleeding. The clinician orders a coagulation panel; the PT is prolonged. The laboratory performs mixing studies and specific clotting factor assays, including a factor X (Stuart–Prower) activity assay billed as 85260 to determine whether factor X deficiency or an inhibitor is present.

Clinical workflow: The specimen (typically citrated plasma) is collected in the outpatient clinic or inpatient ward and transported to the hospital or reference laboratory. A technologist performs screening tests (PT/aPTT). If PT is prolonged and mixing studies suggest a factor deficiency, the lab runs a factor X activity assay. Results are interpreted by a pathologist or clinical laboratory director; the professional component may be reported separately from the technical component. Results inform hematology consultation, further workup for congenital deficiency, acquired deficiency (vitamin K deficiency, liver disease), or presence of an inhibitor, and guide replacement therapy or transfusion decisions.

Coding Specifications

Modifier	Description	When to Use
`26`	Professional component	Use when only the physician/pathologist interpretation is billed separate from the laboratory technical component.
`TC`	Technical component	Use when billing for the laboratory processing and materials only.
`90`	Reference (outside) laboratory	Use when the performed test is sent to an outside reference lab and billed accordingly.
`52`	Reduced services	Use when the test is partially performed or limited relative to the full service.
`53`	Discontinued procedure	Use if specimen collection or test processing was begun but discontinued for documented reasons.
`59`	Distinct procedural service	Not listed in raw modifiers; excluded per input.
`62`	Two surgeons	Rarely applicable; included when two qualified providers share procedural responsibility for complex testing oversight.
`90`	Reference (outside) laboratory	Duplicate entry avoided; only single use is needed.
`91`	Repeat clinical diagnostic lab test	Not listed in raw modifiers; excluded per input.
`95`	Synchronous telemedicine service rendered via real-time interactive audio and video	Use when interpretation or consult occurs via telemedicine and payor allows.
`22`	Increased procedural services	Use when complexity or time for interpretation/consultation is substantially greater than usual.
`52`	Reduced services	Duplicate avoided; only one entry should exist.
`78`	Unplanned return to the operating/procedure room by the same physician following initial procedure for a related procedure during the postoperative period	Rare for lab testing; not commonly used.
`80`	Assistant surgeon	Not typically applicable to laboratory tests.

Taxonomy Code	Specialty	Notes
207RH0000X	Hematology	Hematologists order and interpret coagulation factor testing and manage bleeding disorders.
207K00000X	Pathology	Clinical pathologists oversee laboratory testing, validate assays, and provide professional component reporting.
207L00000X	Clinical Laboratory	Clinical laboratory technologists and directors run and report `85260` as the technical component.
207MR0400X	Transfusion Medicine	Specialists in transfusion medicine manage replacement therapy and interpretation related to factor deficiencies.
207S00000X	Internal Medicine	Hospitalists and internists commonly initiate testing for unexplained coagulopathy and coordinate care.

Related Diagnoses

ICD-10 Code	Description	Clinical Relevance
`D68.4`	Acquired coagulation factor deficiency	Includes acquired factor X deficiency from amyloidosis or inhibitors; directly prompts factor X assay.
`D69.5`	Secondary thrombocytopenia	Bleeding disorders prompting comprehensive coagulation testing including factor assays when indicated.
`D68.6`	Thrombotic microangiopathy	Coagulopathy workup may include factor activity assays in complex cases.
`K72.90`	Hepatic failure, unspecified, without coma	Liver disease causes decreased synthesis of clotting factors; factor X activity may be reduced and tested.
`E83.51`	Vitamin K deficiency	Vitamin K–dependent factor levels (including factor X) are decreased; testing confirms deficiency-related low activity.

Related CPT Codes

CPT Code	Description	Relationship to This Procedure
`85610`	Prothrombin time (PT) and partial thromboplastin time (PTT); plasma thromboplastin components	Often performed as initial screening tests that identify prolonged clotting times prompting `85260`.
`85576`	Thrombin time (TT)	May be performed alongside PT/aPTT to evaluate fibrinogen function when PT is abnormal before specific factor assays.
`85380`	Mixing studies; immediate and incubated	Performed when PT/aPTT is prolonged to distinguish factor deficiency from inhibitor prior to specific factor X assay.
`85305`	Clotting assay, factor activity assay, multiple factors	Related specialized factor activity testing that may be ordered in parallel or as confirmatory testing with `85260`.
`86810`	Blood; clotting factor assay, qualitative	Related to laboratory evaluation of clotting factors and may be part of comprehensive coagulation workup.