Summary & Overview
HCPCS S3855: Genetic Testing for Presenilin-1 Mutations
HCPCS Level II code S3855 denotes genetic testing for mutations in the presenilin-1 (PSEN1) gene, a molecular diagnostic service relevant to evaluation of early-onset familial Alzheimer disease and related neurodegenerative disorders. As a specialized laboratory assay, this code matters nationally because PSEN1 testing informs diagnosis, family risk assessment, and clinical decision-making for affected individuals and their relatives. Coverage and payment policies for specialized genetic tests vary across major payers; this analysis considers national payers including Aetna, Blue Cross Blue Shield, Cigna Health, UnitedHealthcare, and Medicare.
Readers will find a concise overview of the clinical context for PSEN1 testing, typical sites of service, and the types of benchmarks and policy considerations commonly associated with specialized genetic assays. The publication summarizes payer coverage patterns, reimbursement benchmarks where available, and relevant policy updates that affect access to hereditary Alzheimer disease testing. It also outlines what clinicians and billing professionals need to document for claims and highlights common billing and coding considerations specific to high-complexity molecular diagnostics. Data not available in the input is clearly noted where applicable.
Billing Code Overview
HCPCS Level II code S3855 describes genetic testing for detection of mutations in the presenilin - 1 gene. This service involves molecular diagnostic analysis to identify pathogenic or likely pathogenic variants in the PSEN1 gene, which is associated with early-onset familial Alzheimer disease and other neurodegenerative conditions.
Service type: Genetic testing / molecular diagnostic testing
Typical site of service: Clinical genetics laboratory or specialized molecular diagnostics laboratory, with specimen collection typically performed in an outpatient clinic or hospital setting.
Clinical & Coding Specifications
Clinical Context
A 55-year-old patient with a family history of early-onset Alzheimer disease presents to a neurology clinic after multiple first-degree relatives were diagnosed before age 65. The neurologist documents progressive short-term memory decline and orders targeted germline genetic testing for mutations in the presenilin-1 (PSEN1) gene to confirm a pathogenic variant associated with autosomal dominant early-onset familial Alzheimer disease. Pre-test genetic counseling is provided by a genetic counselor or neurologist; informed consent is obtained and a blood sample is collected at an outpatient laboratory or hospital phlebotomy service. The specimen is sent to a certified molecular diagnostics laboratory where DNA sequencing (targeted single-gene sequencing and/or deletion/duplication analysis) is performed. Results are returned to the ordering clinician and genetic counselor; post-test counseling reviews pathogenic, likely pathogenic, or variant of uncertain significance findings and their implications for cascade family testing and care planning. Typical sites of service include outpatient neurology offices, genetic counseling clinics, hospital outpatient laboratories, and reference molecular diagnostic laboratories.
Coding Specifications
| Modifier | Description | When to Use |
|---|---|---|
26 | Professional component | Use when billing only the professional component of genetic testing when applicable (rare for molecular panels but applicable if lab separates professional interpretation). |