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Test Code GBACS Gamma-Amino Butyric Acid Type A (GABA-A) Receptor Antibody by Cell Binding Assay, Serum


Specimen Required


Supplies: Sarstedt Aliquot Tube, 5 mL (T914)

Collection Container/Tube:

Preferred: Red top

Acceptable: SST

Submission Container/Tube: Plastic vial

Specimen Volume: 0.30 mL

Collection Instructions: Centrifuge and aliquot serum into a plastic vial.


Useful For

Evaluating patients with suspected autoimmune encephalitis and autoimmune epilepsy.

Method Name

Cell Binding Assay (CBA)

Reporting Name

GABA-A-R Ab CBA, S

Specimen Type

Serum

Specimen Minimum Volume

0.25 mL

Specimen Stability Information

Specimen Type Temperature Time Special Container
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

Gamma-amino butyric acid type A (GABA-A) receptor autoantibodies are highly predictive of GABA-A receptor autoimmune encephalitis. Seropositive GABA-A receptor encephalitis patients have characteristic clinical-radiologic presentations including frequent seizures and multifocal lesions in the white matter. Majority of patients are treatable with immunotherapy.

Reference Values

Negative

Interpretation

Seropositivity for gamma-amino butyric acid type A receptor autoantibodies supports the clinical diagnosis of autoimmune encephalitis with neurological presentations including seizures and multifocal lesions in the white matter. A search for thymoma cancer, and a trial of immunotherapy should be considered.

Cautions

Negative results do not exclude the diagnosis of autoimmune encephalitis. Only 2% of cases of autoimmune encephalitis are associated with autoantibodies against gamma-amino butyric acid type A receptor.

Clinical Reference

1. O’Connor K, Waters P, Komorowski L, et al. GABAA receptor autoimmunity A multicenter experience. Neurol Neuroimmunol Neuroinflamm 2019;6(3):e552. doi:10.1212/NXI.0000000000000552

2. Spatola M, Petit-Pedrol M, Simabukuro MM, et al. Investigations in GABAA receptor antibody-associated encephalitis. Neurology. 2017; 88(11): 1012–1020. doi:10.1212/WNL.0000000000003713

3. Waters P, Irani S. GABA-A receptor antibodies and their clinical associations. Neurology 2017; 88:1010–1011

4. Petit-Pedrol M, Armangue T, Peng X, et al. Encephalitis with refractory seizures, status epilepticus, and antibodies to the GABAA receptor: a case series, characterization of the antigen, and analysis of the effects of antibodies. Lancet Neurol 2014;13(3):276–286

Method Description

Patient specimen is applied to a composite slide containing transfected and nontransfected HEK-293 cells. After incubation and washing, fluorescein-conjugated goat-antihuman IgG is applied to detect the presence of patient IgG binding.(Package insert: IIFT: Neurology Mosaics, Instructions for the indirect immunofluorescence test. EUROIMMUN, FA_112d-1_A_UK_C13, 02/2019)

Day(s) Performed

Monday through Sunday

Report Available

5 to 10 days

Specimen Retention Time

28 days

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

86255

LOINC Code Information

Test ID Test Order Name Order LOINC Value
GBACS GABA-A-R Ab CBA, S 101874-6

 

Result ID Test Result Name Result LOINC Value
620232 GABA-A-R Ab CBA, S 101874-6

NY State Approved

Yes