The Frequency of Serum Neural Autoantibodies in Suspected Autoimmune Epilepsy (P6.284)

OBJECTIVE: To examine the frequency and age distribution of five serum neuronal autoantibodies to the N-methyl-D-aspartate receptor (NMDA), the voltage-gated potassium channel (VGKC), leucine-rich, glioma-inactivated 1 (LGI1), contactin-associated protein-like 2 (CASPR2), and glutamic acid decarboxylase 65 (GAD65) antigens in specimens sent to a clinical laboratory for an evaluation of autoimmune epilepsy (AE). BACKGROUND: Emerging evidence suggests that a substantial proportion of epilepsy cases, especially those with a poor response to antiepileptic drugs (AED), have an autoimmune basis characterized by the presence of serum neural autoantibodies to the VGKC complex including LGI1 and CASPR2. Early recognition of AE and initiation of immunotherapy may improve patient outcomes. DESIGN/METHODS: Enzyme-linked immunosorbent assays, radioimmunoassays, and immunofluorescence antibody assays were used to detect serum autoantibodies to NMDA receptor, VGKC, LGI1, CASPR2, and GAD65 in specimens (n=77) analyzed for AE at a clinical diagnostic laboratory. The frequencies of these autoantibodies were calculated using de-identified test results. RESULTS: Autoantibodies were identified in 12[percnt] of the population (n=9), but only in specimens from adults (n=59) and not children (n=18). The majority were directed against LGI1 (n=5), followed by GAD65 (n=2), NMDA receptor (n=1), and CASPR2 (n=1). VGKC antibody was borderline in cases positive for CASPR2 and LGI1 antibodies (n=3). Two cases were VGKC antibody negative but LGI1 antibody positive. One case was borderline for VGKC antibody but negative for all other markers. CONCLUSIONS: The frequencies and distributions of autoantibodies differ from previously published studies by the high frequency of autoantibodies to LGI1 and GAD65 and the lack of findings in children. These results suggest that antibodies to the VGKC complex, especially LGI1, are a common cause of AE in adults. Study Supported by: Quest Diagnostics Disclosure: Dr. Sansoucy has received personal compensation for activities with Quest Diagnostics. Dr. Jaremko has received personal compensation for activities with Quest Diagnostics. Dr. Burnham has received personal compensation for activities with Quest Diagnostics. Dr. Mourneau has received personal compensation for activities with Quest Diagnostics. Dr. Goldberger has received personal compensation for activities with Quest Diagnostics. Dr. Patel has received personal compensation for activities with Quest Diagnostics. Dr. Wang has received personal compensation for activities with Quest Diagnostics. Dr. Suer has received personal compensation for activities with Quest Diagnostics. Dr. Batish has received personal compensation for activities with Quest Diagnostics. Dr. Higgins has received personal compensation for activities with Quest Diagnostics.