Summary & Overview
CPT 81166: BRCA1 Large Gene Rearrangement Analysis, Technical Component
CPT code 81166 represents the technical laboratory analysis of the BRCA1 gene to detect large gene rearrangements, specifically deletions and duplications. As a molecular diagnostic technical service, this code captures the laboratory work required to process and analyze specimens for structural variants in BRCA1, a gene clinically associated with hereditary breast and ovarian cancer risk. Nationally, accurate coding for BRCA1 large rearrangement testing affects coverage determinations, claim adjudication, and access to clinically important genetic information.
Key payers in this analysis include Aetna, Blue Cross Blue Shield, Cigna Health, UnitedHealthcare, and Medicare. Readers will find a concise overview of clinical context for BRCA1 large rearrangement testing, typical sites of service, and which payers commonly cover molecular diagnostic laboratory services. The publication summarizes benchmarks and coverage patterns, highlights relevant policy updates where available, and explains how CPT code 81166 is used in billing workflows for the technical component of BRCA1 large rearrangement analysis.
This summary is written for a national audience and is intended to orient billing managers, laboratory directors, and policy analysts to the clinical purpose and payer landscape for CPT code 81166 without offering clinical recommendations.
Billing Code Overview
CPT code 81166 describes a laboratory technical service that analyzes the BRCA1 DNA repair–associated gene (BRCA1) for gene deletions and duplications to detect large gene rearrangements. The description indicates a molecular diagnostic laboratory test focused on identifying structural variants in the BRCA1 gene.
Service type: Molecular diagnostic laboratory test (technical component)
Typical site of service: Clinical laboratory or molecular pathology laboratory (inpatient or outpatient specimen processing and analysis)
Clinical & Coding Specifications
Clinical Context
A patient with a personal or strong family history of breast, ovarian, pancreatic, or prostate cancer is referred for hereditary cancer risk evaluation. A medical geneticist, genetic counselor, or oncologist orders molecular testing to detect large rearrangements (deletions and duplications) in the BRCA1 gene. The specimen is typically a peripheral blood sample collected in an outpatient phlebotomy clinic or ambulatory surgical center and sent to a clinical molecular diagnostics laboratory. The laboratory technologist performs the technical assay (for example, multiplex ligation-dependent probe amplification or next-generation sequencing paired with copy-number analysis) to identify gene deletions and duplications in BRCA1. Results are reported to the ordering clinician and genetic counselor for interpretation, risk assessment, and discussion of management options with the patient. Typical site of service: clinical molecular diagnostic laboratory receiving specimens from outpatient clinics, oncology centers, or hospitals.
Coding Specifications
| Modifier | Description | When to Use |
|---|---|---|
26 | Professional component | When billing only the professional interpretation component separate from the technical lab component (rare for this lab code if technical only). |
TC |