2025 American Academy of Neurology Abstract Website

Chiara Milano¹, Pietro Businaro², Claudia Papi³, Laura Naranjo⁴, Raquel Ruiz Garcia⁴, Lionel Arlettaz⁵, Matteo Gastaldi⁶, Lidia Sabater⁷, Josep Dalmau⁷, Francesc Graus⁸, Marianna Spatola⁷
¹Neuroimmunology Program, Fundació de Recerca Clínic Barcelona-Institut d'Investigacions Biomédiques August Pi i Sunyer (FRCB-IDIBAS), University of Barcelona, Spain; La Caixa Research Institute, Barcelona, Spain; Department of Clinical and Experimental Medicine, University of Pisa, Pisa, Italy, ²Neuroimmunology Program, Fundació de Recerca Clínic Barcelona-Institut d'Investigacions Biomédiques August Pi i Sunyer (FRCB-IDIBAS), University of Barcelona, Spain; University of Pavia and Neuroimmunology research unit, IRCCS Mondino Foundation, ³Neuroimmunology Program, Fundació de Recerca Clínic Barcelona-Institut d'Investigacions Biomédiques August Pi i Sunyer (FRCB-IDIBAS), University of Barcelona, Spain; La Caixa Research Institute, Barcelona, Spain; Department of Neuroscience, Catholic University of the Sacred Heart, Rome, Italy, ⁴Immunology Service, Biomedical Diagnostic Center, Hospital Clínic, Barcelona, Spain, ⁵Service d’Immunologie et Allergologie, Institut Central des Hôpitaux, Hôpital du Valais, Sion, Switzerland, ⁶University of Pavia and Neuroimmunology research unit, IRCCS Mondino Foundation, ⁷Neuroimmunology Program, Fundació de Recerca Clínic Barcelona-Institut d'Investigacions Biomédiques August Pi i Sunyer (FRCB-IDIBAS), University of Barcelona, Spain; La Caixa Research Institute, Barcelona, Spain, ⁸Neuroimmunology Program, Fundació de Recerca Clínic Barcelona-Institut d'Investigacions Biomédiques August Pi i Sunyer (FRCB-IDIBAS), University of Barcelona, Spain

Objective:

To determine the performance of two commercial tissue-based assays (TBAs) to detect autoantibodies against neural intracellular antigens (IC-abs).

Background:

Current strategies to detect IC-abs involve TBAs accompanied by line-blot or cell-based assays (CBAs) to confirm antigen specificity. Most clinical laboratories use commercially available TBAs, but their diagnostic yield has not been assessed.

Design/Methods:

We examined samples from 100 patients with immune-mediated neurological syndromes harbouring IC-abs and from 50 healthy participants. The positivity of IC-abs had been previously established with highly sensitive and specific in-house TBAs accompanied by line blot or CBAs. The 100 patients’ samples included 10 sera of each: Hu, Yo, Ri, SOX1, CV2, Ma2, Tr, amphiphysin, GAD65, and 10 CSF with GFAP antibodies. Two commercial indirect immune-fluorescent TBAs (INOVA and Euroimmun) were assessed. Slides were read by two experienced investigators (JD, FG) blinded from information; discordant results were re-evaluated through interrater discussion.

Results:

The two raters showed substantial agreement (85% for INOVA, 83% for Euroimmun) on negative or positive results. After interrater discussion, they reached an agreement in >95% of cases. INOVA correctly identified 118/150 (79%) samples and misclassified 28/150 (19%): 2 false positive (FP), 26 false negative (FN), whereas Euroimmun correctly identified 105/150 (70%) samples and misclassified 40/150 (27%): 6 FP, 34 FN. Overall, sensitivity was 73% for INOVA and 66% for Euroimmun. Specificity was 96% for INOVA and 88% for Euroimmun. Among the positive samples, antibody-specific immunostaining patterns were correctly identified in 62/100 samples with INOVA and 55/100 with Euroimmun (p=0.39). Both TBAs failed to identify CV2 antibodies. INOVA TBA was better at identifying Ma2 antibodies (9/10 vs. 1/10, p=0.001), while Euroimmun TBA was better at identifying Hu/Ri antibodies (19/20 vs. 12/20, p=0.02).

Conclusions:

This study indicates that the performance of commercial TBAs for IC-abs is suboptimal, particularly for CV2 (both kits), Ma2 (Euroimmun) and Hu/Ri (INOVA) antibodies.