Autoimmune Encephalopathy Evaluation, Serum




Test Mnemonic

ENCSER

CPT Codes

  • 86341 - QTY (1)
  • 86255 - QTY (23)

Includes

  • Neurochondrin IFA, S
  • Septin-7 IFA, S
  • DPPX Ab CBA, S
  • IgLON5 CBA, S
  • PDE10A Ab IFA, S
  • TRIM46 Ab IFA, S
  • AMPA-R Ab CBA, S
  • Amphiphysin Ab, S
  • AGNA-1, S
  • ANNA-1, S
  • ANNA-2, S
  • ANNA-3, S
  • CASPR2-IgG, CBA, S
  • CRMP-5-IgG, S
  • GABA-B-R Ab CBA, S
  • GAD65 Ab Assay, S
  • GFAP IFA, S
  • LGI1-IgG CBA, S
  • mGIuR1 Ab IFA, S
  • NIF IFA, S
  • NMDA-R Ab CBA, S
  • PCA-1, S
  • PCA-2, S
  • PCA-Tr, S
  • Encephalopathy Interpretation, S

Performing Laboratory

Mayo Clinic Dpt of Lab Med & Pathology


Specimen Requirements

Volume Type Container Collect Temperature Transport Temperature Special Instructions
4 mLSerumNo additive (Red) RefrigeratedDraw 2 tubes to ensure adequate serum volume. Patient should have no general anesthetic or muscle-relaxant medications in the previous 24 hours. Specimen collection is recommended before initiation of immunosuppressant medication. This test should not be requested in patients who have recently received radioisotopes (refer to Special Information).

Alternate Specimen Requirements

Volume Type Container Collect Temperature Transport Temperature Special Instructions
4 mLSerumSST (Gold) RefrigeratedDraw 2 tubes to ensure adequate serum volume. Patient should have no general anesthetic or muscle-relaxant medications in the previous 24 hours. Specimen collection is recommended before initiation of immunosuppressant medication. This test should not be requested in patients who have recently received radioisotopes (refer to Special Information).

Minimum Specimen Requirements

Volume Type Container Collect Temperature Transport Temperature Special Instructions
2.5 mL     

Stability

Environmental Condition Description
Refrigerated28 days
Frozen28 days
Ambient72 hours

Days Performed

Sun - Sat

Turnaround Time

11 - 14 days

Methodology

Name Description
Cell Binding Assay (CBA) 
Radioimmunoassay (RIA) 
Immunofluorescence 

Reference Range

CASPR2-IgG CBA Serum
Sex Age From Age To Type Range Range Unit
       Negative 
GAD65 Antibody
Sex Age From Age To Type Range Range Unit
       < or = 0.02 nmol/L 
GFAP IFA S
Sex Age From Age To Type Range Range Unit
       Negative 
LGI1-IgG CBA Serum
Sex Age From Age To Type Range Range Unit
       Negative 
mGluR1 Ab IFA, S
Sex Age From Age To Type Range Range Unit
       Negative 

Special Info

Reflex Algorithm: Each reflex test performed incurs additional charge. If client requests or if the immunofluorescence (IFA) patterns suggest collapsin response-mediator protein-5-IgG (CRMP-5-IgG), then CRMP-5-IgG IFA titer and CRMP-5-IgG Western blot will be performed. If the IFA patterns suggest amphiphysin antibody, then amphiphysin IFA titer and amphiphysin immunoblot will be performed. If the IFA pattern suggests antiglial nuclear antibody (AGNA)-1, then AGNA-1 IFA titer and AGNA-1 immunoblot will be performed. If the IFA pattern suggests antineuronal nuclear antibody type 1 (ANNA-1), then ANNA-1 IFA titer, ANNA-1 immunoblot, and ANNA-2 immunoblot will be performed. If the IFA pattern suggests ANNA-2 antibody, then ANNA-2 IFA titer, ANNA-2 immunoblot, and ANNA-1 immunoblot will be performed. If the IFA pattern suggests Purkinje cytoplasmic antibody type 1 (PCA-1), then PCA-1 IFA titer and PCA-1 immunoblot will be performed. If IFA pattern suggests PCA-Tr antibody, then PCA-Tr IFA titer and PCA-Tr immunoblot will be performed. If IgLON5 cell-binding assay (CBA) is positive, then IgLON5 IFA titer will be performed. If AMPA (alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid) receptor antibody CBA is positive, then AMPA-receptor antibody IFA titer assay will be performed. If gamma-aminobutyric acid B (GABA-B) receptor antibody is positive, then GABA-B-receptor antibody IFA titer assay will be performed. If the IFA pattern suggests glial fibrillary acidic protein (GFAP) antibody, then GFAP IFA titer and GFAP CBA will be performed. If N-methyl-D-aspartate (NMDA) receptor antibody CBA is positive, then NMDA-receptor antibody IFA titer assay will be performed. If DPPX antibody CBA is positive, then DPPX IFA titer will be performed. If the IFA pattern suggests metabotropic glutamate receptor 1 (mGluR1) antibody, then mGluR1 antibody CBA and mGluR1 IFA titer will be performed. If the IFA pattern suggests neuronal intermediate filament (NIF) antibody, then alpha internexin CBA, NIF heavy chain CBA, NIF light chain CBA, and NIF IFA titer will be performed. If the indirect immunofluorescence (IFA) pattern suggests phosphodiesterase 10A (PDE10A) IgG, then the PDE10A antibody IFA titer will be performed. If the indirect immunofluorescence (IFA) pattern suggests tripartite motif-containing protein 46 (TRIM46) IgG, then the TRIM46 antibody cell-binding assay (CBA) and TRIM46 antibody IFA titer will be performed. Neuron-restricted patterns of IgG staining that do not fulfill criteria for ANNA-1, ANNA-2, CRMP-5-IgG, PCA-1, PCA-2, or PCA-Tr may be reported as "unclassified anti-neuronal IgG." Complex patterns that include nonneuronal elements may be reported as "uninterpretable." For optimal antibody detection, specimen collection is recommended prior to initiation of immunosuppressant medication. This test should not be requested in patients who have recently received radioisotopes because of potential assay interference. Specimens will be screened for radioactivity prior to analysis. Radioactive specimens received in the laboratory will be held 1 week and assayed if sufficiently decayed, or canceled if radioactivity remains. Patient should have no general anesthetic or muscle-relaxant drugs in the previous 24 hours. Grossly hemolyzed, lipemic or icteric specimens will be rejected.

Clinical Info

This test is useful for evaluating new onset encephalopathy (noninfectious or metabolic) comprising confusional states, psychosis, delirium, memory loss, hallucinations, movement disorders, sensory or motor complaints, seizures, dyssomnias, ataxias, nausea, vomiting, inappropriate antidiuresis, coma, dysautonomias, or hypoventilation in serum specimens. Diagnosis of autoimmune encephalopathy should be suspected on the basis of clinical course, coexisting autoimmune disorder (eg, thyroiditis, diabetes), serological evidence of autoimmunity, spinal fluid evidence of intrathecal inflammation, neuroimaging or electroencephalographic abnormalities, and favorable response to trial of immunotherapy. Detection of one or more neural autoantibodies aids the diagnosis of autoimmune encephalopathy and may guide a search for cancer. Importantly, autoimmune encephalopathies are reversible. Misdiagnosis as a progressive (currently irreversible) neurodegenerative condition is not uncommon and has devastating consequences for the patient. Clinicians must consider the possibility of an autoimmune etiology in the differential diagnoses of encephalopathy. Neurological accompaniments of neural autoantibodies are generally not syndromic, but diverse and multifocal.

Clinical Limitation

Specimens from pediatric patients are no longer accepted for the Autoimmune Encephalopathy Evaluation. The Autoimmune Pediatric CNS Disorders may be ordered as APCNSS for serum and APCNSC for CSF, or specific antibodies may be ordered directly: GAD65 Antibody, CSF (GADCSF); MOG IgG, Serum (MOGFAC).