Summary & Overview
CPT 0431U: Glycine Receptor Alpha1 IgG Test
CPT code 0431U identifies a Proprietary Laboratory Analyses (PLA) test for Glycine Receptor Alpha1 IgG performed by Mayo Clinic/Mayo Clinic Laboratories. The assay uses a live–cell binding method on cerebrospinal fluid (CSF) or serum and serves as a biomarker for the autoimmune stiff–person spectrum of disorders. Nationally, specialized PLA tests like this are important for accurate diagnosis of rare autoimmune neurologic conditions and have implications for coverage, prior authorization, and laboratory network access.
Key payers covered in this analysis include Aetna, Blue Cross Blue Shield, Cigna Health, UnitedHealthcare, and Medicare. Readers will find a concise overview of clinical context, typical sites of service, and payer inclusion. The publication summarizes benchmarks for coverage and reimbursement where available, highlights relevant policy considerations affecting access to proprietary laboratory tests, and explains the clinical scenarios in which the Glycine Receptor Alpha1 IgG assay is used. The piece also describes coding specifics tied to this PLA code and common modifiers used in practice. Data not available in the input for taxonomies, specific ICD-10 diagnoses, related codes, and detailed payer policy language are noted as unavailable.
Billing Code Overview
CPT code 0431U is a Proprietary Laboratory Analyses (PLA) code that applies only to a single, unique laboratory test performed by Mayo Clinic/Mayo Clinic Laboratories. The test detects Glycine Receptor Alpha1 IgG using a live–cell binding method on cerebrospinal fluid (CSF) or serum specimens. This biomarker is associated with the autoimmune stiff–person spectrum of disorders.
Service type: Specialty laboratory immunologic testing
Typical site of service: Clinical laboratory / reference laboratory; specimens collected in inpatient or outpatient settings and sent to Mayo Clinic Laboratories
Clinical & Coding Specifications
Clinical Context
A patient in their 30s–60s presents to a neurology clinic with progressive axial stiffness, painful spasms, exaggerated startle response, and intermittent autonomic symptoms such as anxiety or respiratory difficulty. The neurologist performs a focused neurologic examination and documents concern for an autoimmune stiff‑person spectrum disorder (including progressive encephalomyelitis with rigidity and myoclonus or classic stiff‑person syndrome). A serum sample is ordered; cerebrospinal fluid (CSF) may be submitted when lumbar puncture is clinically indicated. The clinician orders the specialized antibody test reported with 0431U — Glycine Receptor Alpha1 IgG (Mayo Clinic Laboratories) — to identify IgG autoantibodies targeting the glycine receptor alpha‑1 subunit using a live‑cell binding assay.
Specimen collection: peripheral venous blood in appropriate serum tube; if CSF is being tested, sterile collection and prompt transport to the reference lab. The sample is sent to Mayo Clinic/Mayo Clinic Laboratories with test 0431U ordered and relevant clinical history (stiffness, spasms, startle, suspected autoimmune neurologic disorder) provided. Typical site of service is an outpatient neurology clinic or hospital inpatient unit when evaluation is inpatient; testing is performed by the reference laboratory (off‑site). Results inform diagnosis of glycine receptor–associated autoimmune stiff‑person spectrum disorders and guide immunotherapy decision making and further neurologic workup.
Coding Specifications
| Modifier | Description | When to Use |
|---|---|---|
26 | Professional component | Use when only the professional interpretation of the test is billed separately from the technical component. |
TC | Technical component | Use when only the laboratory technical component (test performance) is billed.
59 | Distinct procedural service | Not provided in raw data; Data not available in the input.
52 | Reduced services | Use when the test is partially performed or specimen insufficient and a reduced service is reported.
53 | Discontinued procedure | Use if specimen collection or testing was discontinued for patient safety or other valid reasons.
90 | Reference (outside) laboratory | Not provided in raw data; Data not available in the input.
QK | Medical direction by a physician; qualified nonphysician anesthesia providers | Not applicable to this PLA test; use for anesthesia services only.
QX | CRNA service with medical direction | Not applicable to this test; anesthesia modifier.
QY | Teaching physician furnished service | Use if a teaching physician is directly involved and billing rules require this modifier (rare for lab tests).
AS | Physician assistant, nurse practitioner, or clinical nurse specialist services furnished in whole or part by a physician assistant, nurse practitioner, or clinical nurse specialist in the ambulatory surgical center | Not commonly used for this lab test.
| Taxonomy Code | Specialty | Notes |
|---|---|---|
207RG0100X | Neurology | Neurologists commonly order glycine receptor antibody testing for suspected stiff‑person spectrum disorders. |
208000000X | Clinical Pathology / Laboratory Medicine | Laboratory medicine specialists oversee testing, quality, and result interpretation at the reference laboratory.
363LP0800X | Neurophysiology | Clinical neurophysiologists or neurodiagnostic specialists may be involved in correlated testing (EMG) though not directly performing the antibody assay.
363A00000X | Neuromuscular Medicine | Specialists in neuromuscular disorders may request this test when autoimmune etiologies of stiffness and spasms are suspected.
Related Diagnoses
| ICD-10 Code | Description | Clinical Relevance |
|---|---|---|
G25.84 | Stiff‑person syndrome | Classic diagnosis associated with glycine receptor alpha‑1 antibodies and the stiff‑person spectrum. |
G25.89 | Other specified extrapyramidal and movement disorders | Used for related hypertonia or rigidity presentations when a specific code is not chosen.
G04.81 | Autoimmune encephalitis | Glycine receptor antibodies can present with encephalitic features overlapping with autoimmune encephalitis.
R25.1 | Tremor, unspecified | May be used for movement abnormalities evaluated during workup for antibody‑mediated disorders.
R25.9 | Unspecified abnormal involuntary movements | Symptom code for spasms or myoclonus prompting antibody testing.
Related CPT Codes
| CPT Code | Description | Relationship to This Procedure |
|---|---|---|
0431U | Glycine Receptor Alpha1 IgG, Mayo Clinic Laboratories (Proprietary Laboratory Analyses) | Primary PLA code for the live‑cell binding assay detecting IgG to glycine receptor alpha‑1 in serum or CSF. |
86038 | Antibody; immunoassay for infectious agents, quantitative or semi‑quantitative, each agent | May be performed in other labs as different immunoassay methodologies; not specific to this PLA but conceptually related lab technique.
86355 | Assay of immunoglobulins or complement (e.g., autoantibodies) by non‑automated method | Related immunologic testing for autoimmune neurology panels; often ordered alongside specific antibody assays.
99213 | Office or other outpatient visit for the evaluation and management of an established patient, typically 15 minutes | Represents a typical neurology outpatient visit during which the clinician documents suspicion for autoimmune stiff‑person disorder and orders 0431U.
62270 | Spinal puncture, diagnostic (lumbar puncture) | If CSF is required for testing, lumbar puncture is performed prior to sending CSF for 0431U.