Anti-Aquaporin 4 (AQP4), Spinal Fluid

Cerebrospinal fluid (CSF)

2 mL

1 mL (Note: This volume does not allow for repeat testing.)

CSF sterile tube

This test is used for evaluation of patients with suspected Neuromyelitis Optica Spectrum Disorder (NMOSD).

Testing for Neuromyelitis Optica (NMO) Spectrum should be considered in patients presenting with optic neuritis, transverse myelitis, and/or area postrema clinical syndrome, which consists of intractable hiccups or nausea and vomiting. NMOSD diagnosis is based on core clinical characteristics, antibody status and features as detected by magnetic resonance neuroimaging. All of these components are included in the International Panel for NMO Diagnosis (IPND) 2015 revised consensus criteria.

Laboratory testing involves determining AQP4 IgG and MOG IgG serum antibody status; the presence of AQP4 or MOG IgG is confirmatory for NMOSDs in the appropriate clinical setting. Cell-based assay (CBA) detection methods are strongly recommended because of their greater sensitivity and specificity when compared with enzyme-linked immunosorbent assays (ELISAs). Patients should be tested during attacks and before beginning immunosuppressive therapy to avoid conversion to a seronegative status.

The absence of AQP4 antibodies does not rule out the diagnosis of NMOSD because false-negative results may occur in the setting of immunosuppression. Occasionally, patients without detectable serum AQP4 IgG are later found to be seropositive; antibody levels increase with clinical relapse and decrease with immunosuppressive therapy. Retesting should be considered before B-cell- or antibody-targeted therapies are instituted and in patients with seronegative results who relapse. AQP4 titers may increase but may not be predictive of relapses or attacks. AQP4 antibodies may become undetectable with immunosuppression, but this does not necessarily indicate clinical response.

Results should not be used as a diagnostic procedure without confirmation of the diagnosis by another medically established diagnostic product or procedure.

This test was developed and its performance characteristics determined by Labcorp. It has not been cleared or approved by the Food and Drug Administration.

Immunofluorescence (IFA)