Summary & Overview
CPT 86366: MuSK Antibody Test for Myasthenia Gravis
CPT code 86366 represents a serologic test for muscle–specific kinase (MuSK) antibodies, commonly performed on serum using methods such as radioimmunoassay. Detection of MuSK antibodies has clinical relevance for diagnosing and characterizing myasthenia gravis, including seronegative or atypical presentations. Nationally, this test informs neurologic diagnosis, treatment selection, and disease monitoring for patients with suspected autoimmune neuromuscular disease.
Key payers covered in this analysis include Aetna, Blue Cross Blue Shield, Cigna Health, UnitedHealthcare, and Medicare. Readers will find an overview of clinical context and typical sites of service, plus benchmarking and coverage considerations where available. The publication summarizes how the test is used in clinical workflows, what service lines and laboratory settings commonly perform it, and which payers often adjudicate claims for this diagnostic assay.
This summary equips clinicians, billing staff, and policy analysts with concise information about CPT code 86366, highlighting its diagnostic purpose, common laboratory setting, and payer landscape. Data not available in the input is noted where relevant, and the piece focuses on national implications rather than jurisdiction-specific policy.
Billing Code Overview
CPT code 86366 tests a patient specimen, such as serum, for muscle–specific kinase (MuSK) antibody using methods like radioimmunoassay. The presence and level of this noninfectious agent antibody can indicate myasthenia gravis (MG), an autoimmune disorder that impairs the nerve–muscle interface and causes muscle weakness.
Service type: Laboratory serologic antibody test
Typical site of service: Clinical laboratory or hospital outpatient laboratory
Data not available in the input.
Clinical & Coding Specifications
Clinical Context
A 45-year-old woman presents to a neuromuscular clinic with progressive fatigable proximal muscle weakness, ptosis, and diplopia. Her neurologist suspects seronegative myasthenia gravis after a negative AChR antibody test and orders testing for muscle-specific kinase (MuSK) antibodies. A phlebotomy draw of serum is collected in the outpatient laboratory; the specimen is sent to a reference immunology lab that performs a radioimmunoassay. The laboratory documents specimen receipt, performs the 86366 assay, validates results, and issues a report to the ordering neurologist. Results positive for MuSK antibodies support the diagnosis of MuSK-positive myasthenia gravis and guide immunotherapy selection and neuromuscular follow-up. Typical sites of service include outpatient clinics, hospital outpatient laboratories, and independent reference laboratories. The service type is a diagnostic serologic immunoassay for a noninfectious agent antibody.
Coding Specifications
| Modifier | Description | When to Use |
|---|---|---|
26 | Professional component | When billing for the physician interpretation component separate from the laboratory technical component |