Summary & Overview
CPT 81184: CACNA1A Expanded Sequence Characterization
CPT code 81184 represents a molecular diagnostic laboratory test that characterizes sequence changes in the CACNA1A gene, typically to detect expanded alleles and other pathogenic variants. This test is clinically important because CACNA1A variants are associated with neurologic conditions such as familial hemiplegic migraine, episodic ataxia, and spinocerebellar ataxia subtypes; accurate molecular characterization supports diagnosis, prognosis, and genetic counseling.
Key payers covered in this analysis include Aetna, Blue Cross Blue Shield, Cigna Health, UnitedHealthcare, and Medicare. Readers will find a national-level overview of clinical context for the test, typical sites of service, common modifiers used with laboratory services, and which payers are commonly involved in coverage decisions. The publication provides benchmarks and policy-focused summaries relevant to billing, coding, and utilization of hereditary and repeat-expansion testing, along with operational considerations for laboratories and billing teams.
The content highlights how CPT code 81184 fits into molecular diagnostic service lines, summarizes common billing practices, and outlines what information is available versus missing. Data not available in the input is explicitly noted where applicable.
Billing Code Overview
CPT code 81184 describes a laboratory technical procedure to characterize sequence changes in the calcium voltage–gated channel subunit alpha1 A gene (CACNA1A). The service targets detection of expanded sequence alleles and other sequence alterations in the CACNA1A gene.
Service Type: Molecular diagnostic laboratory test (genetic testing)
Typical Site of Service: Clinical molecular diagnostic laboratory or reference genetic testing laboratory
Clinical & Coding Specifications
Clinical Context
A 28-year-old patient presents to a neurology clinic with progressive cerebellar ataxia, episodic migraine with aura, and a family history of episodic hemiplegia. The neurologist orders genomic testing for trinucleotide repeat expansions and other pathogenic variants in the CACNA1A gene to characterize suspected allelic expansions associated with episodic ataxia type 2, familial hemiplegic migraine, or spinocerebellar syndromes. A blood specimen is collected in an outpatient phlebotomy suite and sent to a molecular diagnostics laboratory. The laboratory analyst performs the technical assay, typically a targeted expansion analysis or repeat-primed PCR and fragment analysis, to detect expanded sequences and report allele sizes and pathogenicity interpretation. Results are returned to the ordering neurologist, who integrates molecular findings with clinical assessment to guide genetic counseling and management decisions.
Coding Specifications
| Modifier | Description | When to Use |
|---|---|---|
26 | Professional component | Use when billing only the read/interpretation component provided by a pathologist or molecular laboratory director separate from the technical testing. |
TC | Technical component |