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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


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

Not currently performed in house; this test is performed by IIF on transfected fixed cells at University Hospital, Birmingham.