Summary & Overview
CPT 81177: ATN1 Gene Expansion Detection, Molecular Diagnostic Test
CPT code 81177 identifies a laboratory molecular test that detects expanded-repeat mutations in the ATN1 gene, which encodes atrophin 1. This genetic test is clinically significant for diagnosing disorders caused by pathogenic repeat expansions and for confirming a molecular diagnosis when clinical suspicion exists. Nationally, accurate coding for such targeted genetic tests supports appropriate claims processing, clinical documentation, and surveillance of utilization for precision diagnostics.
Key payers included in this analysis are Aetna, Blue Cross Blue Shield, Cigna Health, UnitedHealthcare, and Medicare. Readers will find an overview of the clinical context for ATN1 expansion testing, typical sites of service, common billing modifiers, and the payer mix considered in benchmarking. The content outlines what stakeholders need to know about coding specificity and the role of this test in hereditary neurodegenerative disease evaluation.
The publication explains benchmarks and coverage patterns where available, highlights relevant policy elements affecting molecular diagnostic claims, and situates CPT code 81177 within laboratory service lines and genetic testing workflows. Data not provided in the input are noted as such; this summary focuses on code definition, clinical relevance, payer scope, and the informational categories addressed in the full document.
Billing Code Overview
CPT code 81177 describes a molecular diagnostic laboratory test that detects pathogenic changes in the gene encoding the protein atrophin 1 (ATN1), specifically identifying abnormal alleles with expanded sequences. The service is a genetic testing procedure performed by a laboratory analyst using molecular techniques to evaluate DNA for repeat expansions associated with disease.
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Service type: Genetic/molecular diagnostic testing
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Typical site of service: Clinical diagnostic laboratory (hospital or reference laboratory setting)
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Clinical & Coding Specifications
Clinical Context
A typical patient is an adult with progressive gait disturbance, cognitive decline, psychiatric symptoms, or a family history suggestive of spinocerebellar ataxia or dentatorubral–pallidoluysian atrophy (DRPLA). A neurology clinic evaluates the patient, documents neurologic exam findings (ataxia, dysarthria, myoclonus, or dementia), and orders targeted molecular testing for the ATN1 gene to detect expanded CAG trinucleotide repeats. A specimen (blood or buccal) is collected according to laboratory instructions and sent to a clinical molecular genetics laboratory. The laboratory analyst performs the technical testing using PCR-based repeat sizing, fragment analysis, or triplet-primed PCR to detect abnormal alleles involving expanded sequences in the ATN1 gene. Results are reported to the ordering clinician; if a pathogenic expansion is detected, genetic counseling is arranged. Typical sites of service are an outpatient neurology clinic, hospital outpatient lab, or independent clinical molecular diagnostic laboratory.
Coding Specifications
| Modifier | Description | When to Use |
|---|---|---|
11 | Service performed by the physician | Use when the physician personally performs the professional component of the test (if applicable in-site supervision/documentation supports it). |
22 |