Multiparametric Serological Testing Aids Diagnosis of Autoimmune Encephalitis

Autoimmune encephalitides can manifest with diverse neurological symptoms, including memory deficits, neuropsychiatric conditions and epileptic seizures, and may or may not be associated with cancer.

Timely diagnosis is important, as immediate treatment can prevent irreversible damage to the brain. Particularly in unexplained neurological cases, a comprehensive autoantibody screening can help to establish a diagnosis, enabling rapid commencement of life-saving therapy. Since many of the autoantibody markers are rare, multiparametric screening composed of different transfected-cell substrates is recommended to increase the diagnostic detection rate.

Scientists at the Institute for Experimental Immunology (Euroimmun AG, Lübeck, Germany) tested a cohort that consisted of 2,716 serum samples received between October and December 2010. The samples were tested on a biochip mosaic combining different neuronal tissue sections with monospecific cell substrates for the detection of antibodies against NMDA receptor (NR1), AMPA receptor (GluR1/GluR2), GABAB receptor, LGI1, CASPR2, GAD65, AQP4, and GlyR.

The team found anti-neuronal immunoglobulin G (IgG) in 108 samples with anti-NMDA receptor antibodies being by far the most prevalent finding (38%), followed by anti-LGI1 (11%) and anti-CASPR2 antibodies (11%). In total, more than 60% of the samples were positive for autoantibodies against neuronal surface antigens, while autoantibodies against classical paraneoplastic intracellular antigens were detected in 31%. The high prevalence of autoantibodies against cell surface antigens in CNS underscores the rising relevance of this novel class of neuronal antigens for autoimmune encephalitis diagnostics.

The evaluation of anti-neuronal autoantibodies was then automated using a new function of the established EUROPattern system. The software automatically takes digital images of the substrates and provides a positive/negative classification. The high-resolution images are sharply focussed with the aid of a counterstain, which also serves to verify correct performance of the incubation. The high-quality of the images was verified by comparing on-screen appraisal with visual microscopy using 753 incubations of numerous serum samples sent to a clinical immunology laboratory.

The two evaluation strategies revealed a concordance of 100% with respect to positive/negative discrimination (excluding samples with ambiguous signals at the microscope to avoid inter-reader deviations). The computer-aided immunofluorescence microscopy considerably facilitates the microscopic analysis, supporting laboratory personnel in the rapid issuance of diagnostic findings. This confirmed the high quality of the images and proves that on-screen evaluation offers a satisfying diagnostic accuracy which can compete with classical immunofluorescence microscopy. The study was published originally published on line on August 1, 2016, in the journal Autoimmunity Reviews.

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