Summary & Overview

HCPCS G9843: Ras (KRAS or NRAS) Gene Mutation Testing

HCPCS Level II code G9843 identifies molecular diagnostic testing for Ras family gene mutations (KRAS and NRAS). Nationally, detection of these mutations informs oncology treatment selection, prognostic assessment, and eligibility for targeted therapies and clinical trials. As precision oncology expands, consistent coding for mutation analysis matters for care coordination and reimbursement clarity.

Key payers examined include Aetna, Blue Cross Blue Shield, Cigna Health, UnitedHealthcare, and Medicare. Readers will find a concise overview of coverage patterns, common billing practices, and payer-specific considerations relevant to molecular oncology testing. The publication outlines benchmarks for clinical utilization and coding, summarizes policy updates affecting molecular diagnostic services, and situates G9843 within contemporary clinical workflows for tumor mutation profiling.

This summary provides clinicians, billing professionals, and policy analysts with practical context on the clinical role of RAS mutation testing, anticipated sites of service, and the payer landscape that shapes access and reimbursement for this HCPCS Level II code.

AetnaBlue Cross Blue ShieldCigna HealthUnitedHealthcareMedicareG9843HCPCS Level IImolecular diagnosticsKRASNRASoncology testinggenetic testinglaboratory billing

Billing Code Overview

HCPCS Level II code G9843 denotes testing for Ras (KRAS or NRAS) gene mutation. This service involves molecular diagnostic analysis to detect activating mutations in the RAS family genes that can influence tumor biology and targeted therapy decisions.

Service Type: Molecular diagnostic genetic testing
Typical Site of Service: Hospital outpatient laboratory, independent clinical laboratory, or specialized molecular diagnostics facility

Clinical & Coding Specifications

Clinical Context

A 62-year-old patient with metastatic colorectal adenocarcinoma undergoes tumor genotyping to guide targeted therapy selection. A tumor specimen from a recent CT-guided liver biopsy is submitted to a molecular diagnostics laboratory for analysis of RAS family oncogenes, including KRAS, NRAS, and HRAS as clinically indicated. The workflow includes specimen accessioning, tumor enrichment if needed, DNA extraction, PCR-based or next-generation sequencing (NGS) assays to detect KRAS and NRAS mutations, bioinformatic variant calling, clinical interpretation by a molecular pathologist, and a signed report delivered to the treating medical oncologist. Results indicating an activating KRAS or NRAS mutation inform chemotherapy planning and eligibility for EGFR monoclonal antibody therapies. Typical sites of service include hospital outpatient laboratories, independent clinical reference laboratories, and academic medical center molecular pathology laboratories. Common patient presentation includes progressive metastatic disease or newly diagnosed stage IV colorectal cancer where RAS mutation status is required for therapeutic decision-making.

Coding Specifications

Modifier	Description	When to Use
`22`	Increased procedural services	Use when laboratory service requires substantially greater effort or complexity (rare for molecular tests but applicable for extensive validation or manual review).
`23`	Unusual anesthesia	Not typically applicable to molecular testing; included only when sedation/anesthesia is billed for specimen collection.
`52`	Reduced services	Use when testing is partially reduced (e.g., limited panel run due to insufficient specimen).
`53`	Discontinued procedure	Use when the planned specimen collection or test is started but discontinued for clinical reasons.
`54`	Surgical care only	Use for the surgeon portion of a procedure when separate billing for specimen procurement occurs.
`55`	Postoperative management only	Use when the laboratory or clinician bills only for postoperative follow-up related to biopsy.
`56`	Preoperative management only	Use when only pre-procedure management is billed (e.g., pre-biopsy evaluation).
`62`	Two surgeons	Rare; used when two providers share operative responsibility for specimen procurement.
`AS`	Ambulatory surgical center	Use to indicate service performed in an ambulatory surgical center setting when applicable.
`CO`	Workers' compensation	Use to indicate the claim is related to a workers' compensation payer.
`CQ`	Clinical trial	Use when testing is performed as part of a qualifying clinical trial (investigational device exemption or protocol-specified testing).
`FY`	Item or service furnished pursuant to the Beneficiary-Patient relationship or other payor-specific use	Use per payer instructions when required for reporting payor-specific circumstances.
`FX`	Primary physician no longer treating patient	Use when the ordering physician is no longer the primary treating physician for related care.
`QK`	Medical direction of two, three, or four technician/therapist services	Rare for lab tests; used if medical direction rules apply in ancillary services.
`QX`	Verified by modifier `QK`	Use in conjunction with `QK` per modifier pairing rules.

Taxonomy Code	Specialty	Notes
`207RN0400X`	Medical Oncology	Oncologists order RAS testing for systemic therapy selection.
`207R00000X`	Hematology/Oncology	Multi-disciplinary specialists managing metastatic solid tumors.
`207RX0201X`	Molecular Genetic Pathology	Pathologists who interpret molecular diagnostic assays and sign reports.
`207L00000X`	Pathology	Laboratories and pathologists performing tissue handling and testing.
`363LA2200X`	Laboratory Director (Clinical Molecular Genetics)	Laboratory directors overseeing assay validation and QA/QC.

Related Diagnoses

ICD-10 Code	Description	Clinical Relevance
`C18.9`	Malignant neoplasm of colon, unspecified	Colorectal cancers commonly require `KRAS`/`NRAS` testing to guide anti-EGFR therapy decisions.
`C20`	Malignant neoplasm of rectum	Rectal adenocarcinomas follow the same RAS testing pathways as colon cancer when metastatic or advanced.
`C78.7`	Secondary malignant neoplasm of liver and intrahepatic bile duct	Liver metastases frequently provide tissue for RAS testing in metastatic colorectal cancer.
`C34.90`	Malignant neoplasm of unspecified part of unspecified bronchus or lung	Non-small cell lung cancers may undergo RAS family testing as part of broader molecular profiling in some cases.
`C50.919`	Malignant neoplasm of unspecified site of breast	Breast cancers rarely require RAS testing routinely but may be included in comprehensive panels in certain research or clinical contexts.

Related CPT Codes

CPT Code	Description	Relationship to This Procedure
`81445`	Targeted genomic sequence analysis panel, 5-50 genes (e.g., small cancer gene panels)	Often performed alongside or instead of single-gene RAS testing when broader actionable mutation profiling is required.
`81479`	Unlisted molecular pathology procedure	Used when a specific molecular test does not have an assigned CPT and when billing for a unique or proprietary RAS assay.
`88305`	Level IV surgical pathology, gross and microscopic examination	Billed for tissue processing and histopathologic evaluation of the biopsy specimen prior to molecular testing.
`0004U`	Next-generation sequencing, RAS mutation analysis (example proprietary assay)	Proprietary or analyte-specific CPT Category III codes may be used for certain commercial NGS RAS assays; used when available and appropriate.
`86328`	Immunoassay for tumor markers (example)	Ancillary tests such as immunohistochemistry for tumor characterization may be performed before or concurrent with molecular testing.