GABA-B-Receptor Antibody by CBA, Spinal Fluid
NY State Approved Indicates the status of NY State approval and if the test is orderable for NY State clients.
Evaluating new onset encephalopathy encompassing 1 or more of the following: confusional states, psychosis, delirium, memory loss, hallucinations, seizures, dyssomnias, coma, dysautonomias, or hypoventilation
The following accompaniments should prompt suspicion for autoimmune encephalopathy:
-Autoimmune stigmata (personal or family history, or signs of diabetes mellitus, thyroid disorder, vitiligo, poliosis [premature graying], myasthenia gravis, rheumatoid arthritis, systemic lupus erythematosus)
-History of cancer
-Smoking history (20+ pack years) or other cancer risk factors
-Inflammatory cerebrospinal fluid or isolated protein elevation
-Neuroimaging signs suggesting inflammation
Evaluating limbic encephalitis
Directing a focused search for cancer
Investigating encephalopathy appearing in the course or wake of cancer therapy, and not explainable by metastasis or drug effect
Cell-binding assay (CBA) detects IgG specific for Gamma-Amino Butyric acid-type B receptor (GABA-B-R) by indirect immunofluorescence (IFA)
Reporting Name A shorter/abbreviated version of the Published Name for a test; an abbreviated test name
GABA-B-R Ab CBA, CSF
GABA-B Receptor Ab
Gamma-Aminobutyric Acid Receptor Ab
GABA-B Receptor Ab
Gamma-Aminobutyric Acid Receptor Ab
Specimen Type Describes the specimen type needed for testing
Specimen Required Defines the optimal specimen. This field describes the type of specimen required to perform the test and the preferred volume to complete testing. The volume allows automated processing, fastest throughput and, when indicated, repeat or reflex testing.
Container/Tube: Sterile vial
Specimen Volume: 1 mL
Additional Information: Include relevant clinical information, name, phone number, mailing address, and E-mail address (if applicable) of ordering physician
Specimen Minimum Volume Defines the amount of specimen required to perform an assay once, including instrument and container dead space. Submitting the minimum specimen volume makes it impossible to repeat the test or perform confirmatory or perform reflex testing. In some situations, a minimum specimen volume may result in a QNS (quantity not sufficient) result, requiring a second specimen to be collected.
Mild OK; Gross reject
Mild OK; Gross reject
Mild reject; Gross reject
Specimen Stability Information Provides a description of the temperatures required to transport a specimen to the laboratory. Alternate acceptable temperature(s) are also included.
|CSF||Refrigerated (preferred)||28 days|
Clinical Information Discusses physiology, pathophysiology, and general clinical aspects, as they relate to a laboratory test
Antibody targeting extracellular domains of the B1 subunit of the GABA-B-receptor has been reported in patients with small-cell carcinoma-related autoimmune limbic encephalitis, usually with prominent seizures. Seven of the initially reported 15 patients had 1 or more coexisting antibodies documented in serum: N type calcium channel antibody, 3; GAD65 antibody, 3; thyroid antibodies, 3; AGNA/SOX 1 antibody, 1. A subsequent study reported detecting GABA-B-receptor antibody in the serum of 10 of 70 patients with limbic encephalitis (14%). Testing of cerebrospinal fluid may be helpful when serum testing is negative.
Reference Values Describes reference intervals and additional information for interpretation of test results. May include intervals based on age and sex when appropriate. Intervals are Mayo-derived, unless otherwise designated. If an interpretive report is provided, the reference value field will state this.
GABA-B-receptor IgG is a valuable serological marker of autoimmune encephalopathy and of a patient's immune response to cancer (usually small-cell carcinoma). This autoantibody is usually accompanied by subacute neurological symptoms and signs, and is not found in healthy subjects.
Cautions Discusses conditions that may cause diagnostic confusion, including improper specimen collection and handling, inappropriate test selection, and interfering substances
A negative result does not exclude autoimmune encephalopathy or cancer.
Clinical Reference Provides recommendations for further in-depth reading of a clinical nature
1. Lancaster E, Lai M, Peng X, et al: Antibodies to the GABA(B) receptor in limbic encephalitis with seizures: case series and characterisation of the antigen. Lancet Neurol 2010;9(1):67-76
2. Boronat A, Sabater L, Saiz A, et al: GABA(B) receptor antibodies in limbic encephalitis and anti-GAD-associated neurologic disorders. Neurology 2011;76(9):795-800
Method Description Describes how the test is performed and provides a method-specific reference
Patient cerebrospinal fluid is applied to a composite slide containing transfected HEK293 cells. After incubation and washing, fluorescein-conjugated goat IgG reactive with human IgG is applied to detect bound patient IgG.(Lennon VA, Kryzer TJ, Pittock SJ, et al: IgG marker of optic-spinal multiple sclerosis binds to the aquaporin-4 water channel. J Exp Med 2005;202:473-477)
Day(s) and Time(s) Test Performed Outlines the days and times the test is performed. This field reflects the day and time the sample must be in the testing laboratory to begin the testing process and includes any specimen preparation and processing time required before the test is performed. Some tests are listed as continuously performed, which means assays are performed several times during the day.
Wednesday, Friday; 8 a.m.
Analytic Time Defines the amount of time it takes the laboratory to setup and perform the test. This is defined in number of days. The shortest interval of time expressed is "same day/1 day," which means the results may be available the same day that the sample is received in the testing laboratory. One day means results are available 1 day after the sample is received in the laboratory.
Negative: 2-4 days; Positive: 5-7 days
Specimen Retention Time Outlines the length of time after testing that a specimen is kept in the laboratory before it is discarded
Performing Laboratory Location The location of the laboratory that performs the test
Test Classification Provides information regarding the medical device classification for laboratory test kits and reagents. Tests may be classified as cleared or approved by the US Food and Drug Administration (FDA) and used per manufacturer's instructions, or as products that do not undergo full FDA review and approval, and are then labeled as an Analyte Specific Reagent (ASR), Investigation Use Only (IUO) product, or a Research Use Only (RUO) product.
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 Provides guidance in determining the appropriate Current Procedural Terminology (CPT) code(s) information for each test or profile. The listed CPT codes reflect Mayo Medical Laboratories interpretation of CPT coding requirements. It is the responsibility of each laboratory to determine correct CPT codes to use for billing.
LOINC® Code Information Provides guidance in determining the Logical Observation Identifiers Names and Codes (LOINC) values for the result codes returned for this test or profile.
|Result ID||Reporting Name||LOINC Code|
|61515||GABA-B-R Ab CBA, CSF||In Process|