Adaptor Protein 3 Beta2 (AP3B2) Antibody, Cell-Binding Assay, Serum

Casandra

Casandra Test Code MC75059Version 1 (DRAFT)

Performing Lab

Lab Mayo Clinic LabLab Test ID APBCSCPT Code 86255

Adaptor Protein 3 Beta2 (AP3B2) Antibody, Cell-Binding Assay, Serum

Clinical Use

Use

The test is useful for the differential diagnosis of patients presenting with mixed cerebellar and sensory ataxia and myeloneuropathy. It evaluates AP3B2 (adaptor protein 3 beta2)-IgG by cell-binding assay using serum specimens. AP3B2 (adaptor protein 3 beta2)-IgG is a marker of an autoimmune disorder unified by gait instability as the predominant neurologic presentation. Patients present with either cerebellar, dorsal column, or sensory neuronal dysfunction. Clinical improvement following treatment has been reported. AP3B2 autoimmunity appears rare, is accompanied by ataxia (sensory or cerebellar), and is potentially treatable.

Special Instructions

Only orderable as a reflex. When the indirect immunofluorescence (IFA) pattern suggests AP3B2 (adaptor protein 3 beta2), this test and AP3B2 antibody IFA titer will be performed at an additional charge. The test is part of a broader evaluation for various autoimmune/neuroparaneoplastic disorders using serum specimens from related tests like Axonal Neuropathy, Dysautonomia, Gastrointestinal Dysmotility, Myelopathy, and Movement Disorder evaluations.

Limitations

A positive result supports a diagnosis of neurological autoimmunity. However, a negative result does not exclude neurological autoimmunity or cancer. Neurological phenotypes encountered include cerebellar ataxia, spinocerebellar ataxia, myelopathy, sensory neuronopathy, and autonomic neuropathy. Neurological stabilization or improvement may occur with immune therapy, but not all patients may respond to treatment. The test has not been cleared or approved by the FDA and is consistent with CLIA requirements. Interfering substances and improper specimen collection may lead to diagnostic confusion.

Test Details

New York Approved