Summary & Overview

CPT 84181: Western Blot Protein Fraction Analysis

CPT code 84181 denotes a laboratory Western blot analysis used to separate and evaluate protein fractions in blood or other body fluids. As a specialized protein-detection assay, this code matters nationally because it supports diagnostic confirmation, monitoring of disease-related proteins, and research-directed testing across hospital and clinical laboratories. The code is relevant to clinical laboratories, hospital labs, and specialty diagnostic centers that perform immunoblotting techniques.

Key payers included in this analysis are Aetna, Blue Cross Blue Shield, Cigna Health, UnitedHealthcare, and Medicare. Readers will find an overview of clinical context for using Western blot techniques, national reimbursement and coverage considerations from major commercial and public payers where available, and typical sites of service for the procedure. The publication also summarizes common billing practices for this laboratory service, expected usage scenarios in diagnostic workflows, and operational considerations for laboratories offering immunoblot testing.

This summary provides a national perspective on CPT code 84181, focusing on clinical purpose, payer scope, and the types of information readers can expect in the full publication (benchmarks, policy updates, and clinical context). Data not available in the input are noted where applicable.

AetnaBlue Cross Blue ShieldCigna HealthUnitedHealthcareMedicare84181CPTWestern blotLaboratoryProtein analysisImmunoblotDiagnostic testingClinical laboratory

Billing Code Overview

CPT code 84181 describes a Western blot analysis performed by a laboratory analyst to separate and evaluate the level of various protein fractions in a patient specimen of blood or other body fluid. The test uses the Western blot technique, a laboratory method that detects specific proteins through gel electrophoresis followed by transfer and antibody-based detection.

Service Type: Laboratory diagnostic test (protein separation and analysis)

Typical Site of Service: Clinical laboratory or hospital laboratory

Data not available in the input for payers, associated taxonomies, ICD-10 diagnoses, related codes, and service line.

Clinical & Coding Specifications

Clinical Context

A typical patient is an adult referred from an infectious disease or neurology clinic for confirmatory serologic testing after an initial screening test suggests the presence of disease-specific antibodies. A 42-year-old patient presents with subacute neurologic symptoms and a prior positive/indeterminate ELISA for a suspected infectious or autoimmune condition. The clinician orders a Western blot separation and evaluation of protein fractions from a serum specimen to identify antibody patterns. The clinical workflow: the phlebotomist collects a blood specimen, labels and sends it to the clinical laboratory; a laboratory technologist performs specimen processing and electrophoretic separation, transfers separated proteins to a membrane and probes with patient serum or specific antisera; the lab analyst develops and interprets band patterns; a pathologist or laboratory director signs out the result. Results are reported in the electronic medical record and communicated to the ordering provider for correlation with clinical findings and prior testing.

Coding Specifications

Modifier	Description	When to Use
`26`	Professional component	Use when only the professional interpretation/reporting portion is billed by the physician or pathologist.
`TC`	Technical component	Use when only the laboratory technical component (equipment, technician time, reagents) is billed.
`90`	Reference (outside) laboratory	Use when the test was performed by an outside laboratory and billed by the ordering provider as a reference lab charge.
`91`	Repeat clinical diagnostic test	Use when the test is repeated on the same day for confirmation of prior result.
`59`	Distinct procedural service	Use when multiple distinct laboratory procedures on the same specimen are billed and documentation supports separate services.
`52`	Reduced services	Use when the test was partially reduced or not fully performed.
`53`	Discontinued procedure	Use when testing was started but discontinued for documented clinical reasons.
`90`	(duplicate entry intentionally omitted)	Data not duplicated.
`QW`	CLIA waived test indicator (not in provided list)	Data not available in the input.

Taxonomy Code	Specialty	Notes
207RH0000X	Clinical Pathology	Pathologists who interpret and sign out Western blot results.
207K00000X	Clinical Biochemical Genetics	Laboratory specialists involved in advanced protein testing and interpretation.
364A00000X	Clinical Laboratory	Clinical laboratory technologists and managers who perform the assay.
2080P0800X	Infectious Disease	Ordering clinicians who request confirmatory antibody testing.
2084P0800X	Neurology	Ordering clinicians for neurologic presentations requiring antibody confirmation.

Related Diagnoses

ICD-10 Code	Description	Clinical Relevance
`A54.0`	Gonococcal infection of the cervix	Western blot may be used in research or specialized serologic evaluation for complicated infections.
`B20`	Human immunodeficiency virus [HIV] disease	Western blot historically used as confirmatory HIV testing to identify specific viral proteins.
`G61.0`	Guillain-Barré syndrome	Western blot can be used in evaluation of antibody-mediated neuropathies when specific antigen testing is needed.
`M32.9`	Systemic lupus erythematosus, unspecified	Autoimmune serology including Western blot for specific autoantibodies in specialized labs.
`R56.9`	Seizure, unspecified	When autoimmune or infectious etiologies are considered, protein-specific assays including Western blot can aid diagnosis.

Related CPT Codes

CPT Code	Description	Relationship to This Procedure
`80053`	Comprehensive metabolic panel	Performed as part of initial laboratory evaluation; may be ordered alongside to assess organ function prior to interpretation.
`81025`	Urine pregnancy test, non-automated, with direct observation	Not directly related; Data not available in the input.
`87220`	Culture, bacterial, smear, and trichrome staining (example)	Performed in parallel when infectious etiologies require culture and molecular confirmation.
`86308`	Immunoassay for infectious agent antibody, qualitative or semiquantitative, single step method	Often used as initial screening serologic tests preceding confirmatory Western blot.
`88360`	Immunohistochemistry, per specimen; first stain	Used when tissue-based immunoassays are needed in conjunction with serum Western blot for diagnostic correlation.