Autoimmune Encephalitis Antibodies (LGI1, CASPR2, NMDA, DPPX, AMPA1/2, GABA B)
| Category | Immunology |
|---|---|
| Test background |
The autoimmune encephalitidies are immune-mediated brain disorders that often present rapidly (<3 months) with short-term memory loss, altered mental state and/or psychiatric symptoms. Other diagnostic features include new onset seizures with or without CSF pleocytosis and MRI features of encephalitis (Graus F, et al. Lancet Neurol. 2016 Apr;15(4):391-404). Some are a paraneoplastic phenomenon. Rapid diagnosis and early instigation of immunosuppression are associated with improved long term outcomes. The below table lists the most common autoantibodies found in autoimmune encephalitis in descending order of frequency, those in bold are included in the autoimmune encephalitis screen. Table adapted from Uy CE, Binks S, Irani SR. Autoimmune encephalitis: clinical spectrum and management. Practical Neurology 2021;21:412-423 Antibodies should be measured in CSF and serum. Any positive serum result should always be confirmed in CSF to reduce the risk of misdiagnosis (Dalmau J, Graus F. JAMA Neurol. 2023 Jan 1;80(1):12-14.) This test detects antibodies to a panel of neuronal cell surface antigens including the glutamate receptors NMDAR and AMPA1/2, GABAB receptors, DPPX and the voltage gated potassium channel VGKC-associated proteins LGI1 and CASPR2. See also Neuronal (paraneoplastic) antibody screen, MOG, Aquaporin, glycine receptor antibodies. 
|
| Clinical Indications |
The differential diagnosis of encephalitis when alternative causes (infection, neoplasm, etc.) have been excluded. |
| Reference range | Negative |
| Sample & container required | CSF & Serum RST (rust top or SST yellow top) |
| Sample volume | 5-10 mL blood (2 mL serum), 0.5ml CSF |
| Turnaround time | 14 days, for urgent requests please liaise with the consultant clinical scientist |
| Notes | Not currently performed in house; this test is performed by IIF on transfected fixed cells at University Hospital, Birmingham. |