CPT 85378: D-dimer Assay on Blood or Plasma

CPT code 85378 represents a laboratory diagnostic assay for D‑dimer performed on blood or plasma to detect clinically significant levels of fibrin degradation products. D‑dimer testing plays a key role in evaluating patients for thromboembolic conditions and in risk stratification for clotting disorders, making it an important component of laboratory medicine and acute care pathways nationwide. This publication covers national payer practices for common commercial plans and Medicare, noting coverage considerations and how D‑dimer testing fits into clinical workflows.

Key payers included in the review are Aetna, Blue Cross Blue Shield, Cigna Health, UnitedHealthcare, and Medicare. Readers will find a concise explanation of the clinical context for D‑dimer testing, typical sites of service, and the service type associated with the code. The report also summarizes available benchmarks and common billing practices where available, highlights recent policy updates that affect laboratory testing coverage, and outlines coding and billing considerations relevant to laboratories and hospital billing departments.

Data not available in the input is explicitly noted where applicable. The content is intended for national audiences including laboratory managers, coding specialists, and policy analysts seeking a practical overview of CPT code 85378 and its role in modern clinical care.

Billing Code Overview

CPT code 85378 describes a laboratory test performed on a patient’s blood or plasma to detect D‑dimer at clinically significant levels. The test is used to assess the presence of fibrin degradation products that can indicate abnormal clot formation and breakdown.

Service type: Laboratory diagnostic test (D‑dimer assay)

Typical site of service: Clinical laboratory or hospital laboratory (blood or plasma specimen collection)

Clinical Context

A 58-year-old woman presents to the emergency department with acute-onset unilateral leg swelling and pleuritic chest pain. The emergency physician obtains a focused history and performs vitals, then orders laboratory testing to evaluate for venous thromboembolism. A blood sample is collected and sent to the hospital clinical laboratory for a quantitative D‑dimer assay (85378) to determine whether fibrin degradation products are present at clinically significant levels. The laboratory technologist performs the assay on plasma using an immunoassay platform and reports a numeric D‑dimer value with the lab result. Results are routed to the ordering clinician; an elevated D‑dimer in this clinical context supports further diagnostic imaging (for example, duplex ultrasound of the leg or CT pulmonary angiography), while a normal D‑dimer may support ruling out acute pulmonary embolism or deep vein thrombosis in patients with low pretest probability.

Coding Specifications

Modifier	Description	When to Use
`26`	Professional component	Use when billing only the physician interpretation/report component separate from the technical lab processing (rare for automated assays).
`TC`

Taxonomy Code	Specialty	Notes
207RG0100X	Clinical Pathology	Laboratory directors and pathologists overseeing D‑dimer testing and result validation.
207L00000X	Clinical Laboratory	Clinical laboratory technologists and managers performing assay processing.
207P00000X	Laboratory Practitioner	Specialists involved in laboratory operations and quality control.

Related Diagnoses

ICD-10 Code	Description	Clinical Relevance
`I82.401`	Acute embolism and thrombosis of unspecified deep veins of right lower extremity	D‑dimer used to evaluate suspected deep vein thrombosis.
`I26.99`	Other pulmonary embolism without acute cor pulmonale	D‑dimer supports evaluation for pulmonary embolism and guides imaging decisions.
`R06.02`	Shortness of breath	Non-specific symptom prompting D‑dimer when thromboembolism is considered.
`R22.42`	Localized swelling, mass and lump, left lower limb	Limb swelling raises concern for DVT; D‑dimer assists triage.
`R07.9`	Chest pain, unspecified	Pleuritic chest pain may prompt D‑dimer as part of PE workup.

Related CPT Codes

CPT Code	Description	Relationship to This Procedure
`36415`	Collection of venous blood by venipuncture	Blood specimen collection performed immediately prior to `85378`.
`73721`	Magnetic resonance (MR) angiography, any joint, without contrast (example placeholder)	Data not available in the input.
`71260`	CT angiography, chest, with contrast material (used for pulmonary embolism evaluation)	Often performed after an elevated `85378` when clinical suspicion for pulmonary embolism remains.
`93970`	Duplex scan of extremity veins, complete bilateral study	Performed after a positive D‑dimer to evaluate for deep vein thrombosis.
`36416`	Collection of capillary blood specimen (finger/heel)	Alternative specimen collection method when venipuncture is not feasible prior to `85378`.

OpenPayer

Summary & Overview