Summary & Overview
CPT 81180: ATXN3 (Ataxin 3) Repeat Expansion Detection
CPT code 81180 represents a technical molecular diagnostic test to detect expanded sequence alleles in the ataxin 3 gene (ATXN3). This genetic test is used in the laboratory to identify pathogenic repeat expansions that are associated with neurogenetic conditions. As a targeted molecular assay, the technical component captured by this code is important for laboratories reporting genetic diagnostics and for payers managing coverage of specialty molecular testing nationally.
Key payers covered in this analysis include Aetna, Blue Cross Blue Shield, Cigna Health, UnitedHealthcare, and Medicare. The summary addresses coverage patterns and payment benchmarks across major commercial plans and Medicare, and provides clinical context for use of ATXN3 expansion testing.
Readers will learn what CPT code 81180 represents, typical settings where the test is performed, and the clinical indication for detecting ATXN3 expanded alleles. The publication also provides an overview of payer coverage considerations, common billing modifiers and service line placement, and benchmark topics relevant to laboratories and billing professionals. Data not available in the input will be noted where applicable.
Billing Code Overview
CPT code 81180 describes a technical laboratory procedure to detect changes in the ataxin 3 gene (ATXN3) and identify abnormal alleles with expanded sequences. The service is a molecular genetic test focused on detecting pathogenic repeat expansions in the ATXN3 gene.
Service Type: Genetic molecular diagnostic test (technical component)
Typical Site of Service: Clinical molecular diagnostics laboratory or hospital laboratory
Clinical & Coding Specifications
Clinical Context
A typical patient is an adult with progressive cerebellar ataxia, slurred speech, gait instability, and a family history suggestive of spinocerebellar ataxia. A neurology clinic visit includes history, neurologic exam, and discussion of genetic testing options. The clinician orders targeted molecular testing for the ATXN3 (ataxin‑3) gene to detect expanded CAG trinucleotide repeats associated with spinocerebellar ataxia type 3 (SCA3/Machado–Joseph disease). A peripheral blood sample is collected in the clinic or phlebotomy center; the specimen is sent to a molecular diagnostics laboratory. In the lab, a molecular technologist performs the technical assay (fragment analysis, PCR sizing, or repeat‑primed PCR) to determine repeat length and presence of expanded alleles. The laboratory issues a report documenting repeat counts, interpretation (normal, intermediate, or pathogenic expansion), and method used. Results are returned to the ordering neurologist and genetic counselor for clinical correlation and family counseling. Typical site of service: outpatient neurology clinic, genetic counseling clinic, or reference molecular diagnostics laboratory.
Coding Specifications
| Modifier | Description | When to Use |
|---|---|---|
26 | Professional component | Use when separately reporting the physician or molecular pathologist's interpretation/report while the laboratory bills the technical component separately. |