Sign in →

Test Code NMOCS Neuromyelitis Optica (NMO)/Aquaporin-4-IgG Cell-Binding Assay, Serum


Advisory Information


This test is only available for NYS patients. For all other locations, see NMOFS / Neuromyelitis Optica (NMO)/Aquaporin-4-IgG Fluorescence-Activated Cell Sorting (FACS) Assay, Serum.



Specimen Required


Container/Tube:

Preferred: Red top

Acceptable: Serum gel

Specimen Volume: 1 mL

Additional Information: Include relevant clinical information, name, phone number, mailing address, and email address (if applicable) of ordering physician.


Secondary ID

61715

Useful For

This test is only available for NYS patients. For all other locations, see NMOFS / Neuromyelitis Optica (NMO)/Aquaporin-4-IgG Fluorescence-Activated Cell Sorting (FACS) Assay, Serum

 

Diagnosis of a neuromyelitis optica spectrum disorder (NMOSD)

 

Distinguishing NMOSD from multiple sclerosis early in the course of disease

Method Name

Cell-Binding Assay (CBA) Detects IgG Specific for AQP4 (M1 isoform) by Indirect Immunofluorescence Assay (IFA)

Reporting Name

NMO/AQP4-IgG CBA, S

Specimen Type

Serum

Specimen Minimum Volume

0.5 mL

Specimen Stability Information

Specimen Type Temperature Time
Serum Refrigerated (preferred) 28 days
  Frozen  28 days
  Ambient  72 hours

Reject Due To

Hemolysis

Mild OK; Gross reject

Lipemia

OK

Icterus

Mild reject; Gross reject

Other

NA

Clinical Information

Neuromyelitis optica (NMO), sometimes called Devic disease, is a severe, relapsing, autoimmune inflammatory, and demyelinating central nervous system disease that predominantly affects optic nerves and the spinal cord. The disorder is now recognized as a spectrum of autoimmunity targeting the astrocytic water channel aquaporin-4 (AQP4). NMO spectrum disorders (NMOSD) may involve the brain and brainstem with symptoms of encephalopathy (particularly in children). The initial symptoms may be bouts of intractable nausea and vomiting. Magnetic resonance imaging typically reveals large inflammatory spinal cord lesions involving 3 or more vertebral segments. During acute attacks, the cerebrospinal fluid contains inflammatory cells, but usually lacks evidence of intrathecal IgG synthesis. The clinical course is characterized by relapses of optic neuritis or transverse myelitis, or both.

 

Prior to introducing a serological biomarker for NMO, the disorder was thought to be confined exclusively to the optic nerves and spinal cord, that the clinical course was monophasic, and that NMO was a subset of multiple sclerosis (MS). The discovery of a highly specific disease marker for NMO, NMO-IgG/AQP4-IgG  helped to define the full clinical spectrum of NMOSD and distinguish these disorders from MS.

 

Many patients with NMOSD are misdiagnosed as having MS. Importantly, the prognosis and optimal treatments for the 2 diseases differ. NMOSD typically has a worse natural history than MS, with frequent and early relapses. NMOSD attacks are often severe resulting in a rapid accumulation of disability (blindness and paraplegia). Within 5 years, 50% of patients lose functional vision in at least 1 eye or are unable to walk independently. Treatments for NMOSD include corticosteroids and plasmapheresis for acute attacks and mycophenolate mofetil, azathioprine, and rituximab for relapse prevention. Beta-interferon, a treatment promoted for MS, exacerbates NMOSD. Therefore, early diagnosis and initiation of NMO-appropriate immunosuppressant treatment is important to optimize the clinical outcome by preventing further attacks.

 

Detection of NMO IgG by cell-binding assay allows distinction of NMOSD (73% are positive) from MS (0% positive), and is indicative of a relapsing disease, mandating initiation of immunosuppression, even after the first attack, thereby reducing attack frequency and disability in the future.

Reference Values

Negative

Interpretation

A positive value is consistent with a neuromyelitis optica spectrum disorder (NMOSD) and justifies initiation of appropriate immunosuppressive therapy at the earliest possible time. This allows early initiation and maintenance of optimal therapy. Recommend follow-up in 6 months if NMOSD is suspected. This autoantibody is not found in healthy subjects.

Clinical Reference

1. Waters P, McKeon A, Leite MI, et al: Multicenter comparison of aquaporin-4 IgG assays in NMO spectrum disorders. Neurology 2012;78:665-671

2. Lennon VA, Wingerchuk DM, Kryzer TJ, et al: A serum autoantibody marker of neuromyelitis optica; distinction from multiple sclerosis. Lancet 2004;364:2106-2112

Day(s) and Time(s) Performed

Sunday 8:00 AM, Monday-Thursday 3:00 PM

Analytic Time

5 days

Performing Laboratory

Mayo Medical Laboratories in Rochester

Test Classification

This test was developed and its performance characteristics determined by Mayo Clinic in a manner consistent with CLIA requirements. This test has not been cleared or approved by the U.S. Food and Drug Administration.

CPT Code Information

86255

LOINC Code Information

Test ID Test Order Name Order LOINC Value
NMOCS NMO/AQP4-IgG CBA, S 43638-6

 

Result ID Test Result Name Result LOINC Value
61715 NMO/AQP4-IgG CBA, S 63439-4