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Test Code GFATS Glial Fibrillary Acidic Protein Alpha Subunit Antibody, Immunofluorescence Titer Assay, Serum (Non-Orderable)


Necessary Information


Provide the following information:

-Relevant clinical information

-Ordering healthcare professional name, phone number, mailing address, and email address



Specimen Required


Only orderable as a reflex. For more information see PNEFS / Neuroimmunology Antibody Follow-up, Serum.

 

Supplies: Sarstedt Aliquot Tube, 5 mL (T914)

Collection Container/Tube:

Preferred: Red top

Acceptable: Serum gel

Submission Container/Tube: Plastic vial

Specimen Volume: 4 mL Serum

Collection Instructions: Within 2 hours of collection, centrifuge and aliquot serum into a plastic vial.


Secondary ID

605133

Useful For

Only orderable as a reflex. For more information see PNEFS / Neuroimmunology Antibody Follow-up, Serum.

 

Reporting an end titer result in serum specimens

 

Distinguishing autoimmune glial fibrillary acidic protein (GFAP) astrocytopathy from infectious meningoencephalitis and idiopathic inflammatory central nervous system disorders, such as multiple sclerosis, vasculitis and sarcoidosis, disorders commonly considered in the differential diagnosis

 

Alerting the clinician that the patient has an immune-mediated, steroid-responsive disorder and to search for a malignancy

Testing Algorithm

If immunofluorescence assay (IFA) pattern suggests glial fibrillary acidic protein (GFAP), then the GFAP IFA titer and GFAP cell-binding assay are performed at an additional charge.

Method Name

Only orderable as a reflex. For more information see PNEFS / Neuroimmunology Antibody Follow-up, Serum.

 

Indirect Immunofluorescence Assay (IFA)

Reporting Name

GFAP IFA Titer, S

Specimen Type

Serum

Specimen Minimum Volume

Serum: 1 mL

Specimen Stability Information

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

Reject Due To

Gross hemolysis Reject
Gross lipemia Reject
Gross icterus Reject

Clinical Information

Glial fibrillary acidic protein (GFAP)-IgG is a biomarker of a subacute, progressive autoimmune meningitis, encephalitis, and myelitis. These disorders may mimic multiple sclerosis or other idiopathic inflammatory central nervous system disorders, such as sarcoidosis. Neurologic manifestations include headache, optic neuropathy, transverse myelitis, cognitive decline, and cerebellar ataxia. Cerebrospinal fluid findings are inflammatory. Cranial magnetic resonance imaging reveals linear perivascular enhancement oriented radially to the ventricles. A paraneoplastic neurologic association is common. Reported neoplasms accompanying neurologic symptoms include adenocarcinomas of the prostate and gastroesophageal tract, myeloma, melanoma, colonic carcinoid, parotid pleomorphic adenoma, and teratoma. If GFAP-IgG is detected by immunofluorescence assay, testing for the alpha isoform of GFAP (GFAPalpha-IgG) by cell-based assay is performed.

Reference Values

Only orderable as a reflex. For more information see PNEFS / Neuroimmunology Antibody Follow-up, Serum.

 

<1:240

Interpretation

Seropositivity for autoantibody (positive) is supportive of autoimmune glial fibrillary acidic protein (GFAP) astrocytopathy, a treatable form of meningoencephalomyelitis. A paraneoplastic basis should be considered, according to age, sex, and other risk factors.

 

Patients who are GFAP-IgG positive have increased risk of tumor. GFAP-IgG increases the likelihood of certain malignancies being found within 2 years of symptom onset (34%). The most common malignancy found is ovarian teratoma (22%).

 

Glial fibrillary acidic protein meningoencephalomyelitis is immunotherapy responsive. GFAP-IgG positive patients have better outcomes after treatment with corticosteroids.

 

The presence of GFAP-IgG alerts the clinician that the patient has an immune-mediated, steroid-responsive disorder and directs patient care accordingly. It also alerts the clinician to search for a malignancy.

Method Description

The patient's specimen is tested by a standardized immunofluorescence assay that uses a composite frozen section of mouse cerebellum, kidney, and gut tissues. After incubation with the specimen and washing, fluorescein-conjugated goat-antihuman IgG is applied. Neuron-specific autoantibodies are identified by their characteristic fluorescence staining patterns. Specimens that are scored positive for any neuronal nuclear or cytoplasmic autoantibody are titrated. Interference by coexisting non-neuron-specific autoantibodies can usually be eliminated by serologic absorption.(Honorat JA, Komorowski L, Josephs KA, et al. IgLON5 antibody: Neurological accompaniments and outcomes in 20 patients. Neurol Neuroimmunol Neuroinflamm. 2017;4[5]:e385. doi:10.1212/NXI.0000000000000385)

Day(s) Performed

Monday through Sunday

Performing Laboratory

Mayo Clinic Laboratories in Rochester

Test Classification

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

CPT Code Information

86256

LOINC Code Information

Test ID Test Order Name Order LOINC Value
GFATS GFAP IFA Titer, S 93423-2

 

Result ID Test Result Name Result LOINC Value
605133 GFAP IFA Titer, S 93423-2