Summary & Overview

CPT 81274: Huntingtin (HTT) Gene Repeat Characterization

CPT code 81274 represents a molecular diagnostic assay that characterizes nucleotide repeat expansions in the huntingtin gene (HTT). This test is used after an expanded allele is detected to determine repeat length and confirm the genetic basis of Huntington disease or related presentations. Nationally, accurate HTT repeat characterization supports diagnostic certainty, informs genetic counseling, and guides clinical management and care planning for affected individuals.

Key payers commonly referenced for coverage and reimbursement include Aetna, Blue Cross Blue Shield, Cigna Health, UnitedHealthcare, and Medicare. Readers will find a concise overview of the clinical purpose of the test, typical sites where the service is performed, and the operational context for billing this laboratory procedure. The publication summarizes common modifiers and payer interactions for lab-based molecular diagnostics, highlights national-level benchmarks for billing practice where available, and outlines relevant coding relationships.

This resource is intended to help billing professionals, laboratory managers, and policy analysts understand the clinical role of CPT code 81274, the payer landscape, and the practical context for submitting claims and interpreting coverage policies at a national level. Data not available in the input is noted where applicable.

AetnaBlue Cross Blue ShieldCigna HealthUnitedHealthcareMedicareCPT 81274molecular diagnosticsgenetic testinghuntington diseaseHTT genelaboratory billinggenetic counselingclinical laboratorytrinucleotide repeat

Billing Code Overview

CPT code 81274 describes a laboratory test that characterizes changes in the huntingtin gene (HTT), typically to identify nucleotide repeat lengths after an expanded allele has been detected. This is a molecular diagnostic procedure performed by a clinical laboratory analyst to determine the number and nature of CAG trinucleotide repeats in the HTT gene.

Service Type: Genetic / Molecular Diagnostic Testing

Typical Site of Service: Clinical laboratory or specialized molecular diagnostics laboratory

Clinical & Coding Specifications

Clinical Context

A 35-year-old adult with a family history of Huntington disease presents to a genetic counseling clinic after a relative was diagnosed with an expanded CAG repeat in the huntingtin gene (HTT). The clinician orders molecular testing to characterize HTT allele repeat size to confirm or exclude the pathogenic expanded allele. Blood is collected in an EDTA tube and sent to a molecular diagnostics laboratory. The laboratory performs DNA extraction, PCR-based sizing or triplet-primed PCR and capillary electrophoresis to determine the number of CAG repeats and report whether alleles fall in normal, intermediate, reduced-penetrance, or pathogenic ranges. Results are returned to the ordering physician and genetic counselor to support diagnosis, prognostication, and family planning discussions. Typical site of service is an outpatient genetic testing laboratory or hospital molecular pathology lab; specimen collection occurs in an outpatient clinic or draw station.

Coding Specifications

Modifier	Description	When to Use
`26`	Professional component	Use when billing physician or pathologist interpretation separate from the laboratory technical component.
`TC`	Technical component

Taxonomy Code	Specialty	Notes
2080P0200X	Medical Genetics	Physicians specializing in clinical genetics ordering and interpreting HTT testing.
207K00000X	Pathology	Molecular pathology/performance of test interpretation and sign-out.
174400000X	Clinical Laboratory	Clinical laboratory scientists and molecular technologists performing the technical assay.
208D00000X	Neurology	Neurologists ordering confirmatory testing for patients with movement disorders.
363LP0800X	Genetic Counselor	Genetic counselors coordinating testing, consent, and result disclosure.

CPT Code	Description	Relationship to This Procedure
`81275`	Huntington disease; analysis of expanded allele, confirmatory testing or repeat testing for HTT CAG repeat	Often performed if initial testing requires confirmation or further characterization of expanded allele size.
`81223`	SMN1, SMN2 (spinal muscular atrophy) analysis; gene-level testing	Example of other neurologic genetic testing often ordered by the same clinicians; performed in similar molecular labs.
`81479`	Unlisted molecular pathology procedure	Used when a specific molecular test does not have an established code; occasionally used for novel or custom HTT assays not captured by existing codes.
`88360`	Immunohistochemistry, each additional single or multiple antibody stain	Not directly related to HTT sizing; Data not available in the input.
`81270`	Myotonic dystrophy type 1, DMPK gene; analysis of CTG repeat expansion	Analogous repeat-expansion testing workflow and lab techniques; often performed in same labs.

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