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Research paper
Multicentre comparison of a diagnostic assay: aquaporin-4 antibodies in neuromyelitis optica
  1. Patrick Waters1,
  2. Markus Reindl2,
  3. Albert Saiz3,
  4. Kathrin Schanda2,
  5. Friederike Tuller2,
  6. Vlastimil Kral4,
  7. Petra Nytrova5,
  8. Ondrej Sobek6,
  9. Helle Hvilsted Nielsen7,
  10. Torben Barington7,
  11. Søren T Lillevang7,
  12. Zsolt Illes8,9,
  13. Kristin Rentzsch10,
  14. Achim Berthele11,
  15. Tímea Berki12,
  16. Letizia Granieri13,
  17. Antonio Bertolotto13,
  18. Bruno Giometto14,
  19. Luigi Zuliani14,
  20. Dörte Hamann15,
  21. E Daniëlle van Pelt16,
  22. Rogier Hintzen16,
  23. Romana Höftberger3,17,
  24. Carme Costa18,
  25. Manuel Comabella18,
  26. Xavier Montalban18,
  27. Mar Tintoré18,
  28. Aksel Siva19,
  29. Ayse Altintas19,
  30. Günnur Deniz20,
  31. Mark Woodhall1,
  32. Jacqueline Palace1,
  33. Friedemann Paul21,
  34. Hans-Peter Hartung22,
  35. Orhan Aktas22,
  36. Sven Jarius23,
  37. Brigitte Wildemann23,
  38. Christian Vedeler24,25,
  39. Anne Ruiz26,
  40. M Isabel Leite1,
  41. Peter Trillenberg27,
  42. Monika Probst28,
  43. Sandra Saschenbrecker10,
  44. Angela Vincent1,
  45. Romain Marignier26
  1. 1Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, UK
  2. 2Clinical Department of Neurology, Medical University of Innsbruck, Innsbruck, Austria
  3. 3Neuroimmunology Program, Hospital Clinic and Institut d'Investigació Biomèdica August Pi i Sunyer (IDIBAPS), Universitat de Barcelona, Barcelona, Spain
  4. 4Zdravotni ustav se sidlem v Usti nad Labem, Centrum imunologie a mikrobiologie, Usti nad Labem, Czech Republic
  5. 5Department of Neurology, Center of Clinical Neuroscience First Faculty of Medicine, General University Hospital and First Faculty of Medicine, Charles University in Prague, Prague, Czech Republic
  6. 6Laboratory for CSF and Neuroimmunology, Topelex Ltd, Prague, Czech Republic
  7. 7Department of Clinical Immunology, Odense University Hospital, Odense, Denmark
  8. 8Institute of Clinical Research, University of Southern Denmark, Odense, Denmark
  9. 9Department of Neurology, University of Pécs, Pécs, Hungary
  10. 10Euroimmun AG, Lübeck, Germany
  11. 11Klinikum rechts der Isar der TU München, Klinik für Neurologie, Munich, Germany
  12. 12Department of Immunology and Biotechnology, University of Pécs, Pécs, Hungary
  13. 13Clinical Neurobiology Unit, Neuroscience Institute Cavalieri Ottolenghi (NICO), University Hospital San Luigi Gonzaga, Regional Referring Multiple Sclerosis Centre, Orbassano, Italy
  14. 14Department of Neurology, Azienda ULSS 9 Treviso, Treviso, Italy
  15. 15Sanquin Diagnostic Services, Department of Immunopathology and Blood Coagulation, Amsterdam, The Netherlands
  16. 16Department of Neurology, MS Centre ErasMS, Erasmus MC, Rotterdam, The Netherlands
  17. 17Institute of Neurology, Medical University of Vienna, Vienna, Austria
  18. 18Servei de Neurologia-Neuroimmunologia, Centre d'Esclerosi Múltiple de Catalunya (Cemcat), Vall d'Hebron Institut de Recerca, Hospital Universitari Vall d'Hebron, Universitat Autònoma de Barcelona, Barcelona, Spain
  19. 19Neurology Department, Istanbul University, Cerrahpasa Medical School, Istanbul, Turkey
  20. 20Department of Immunology, Istanbul University, Institute of Experimental Medicine, Istanbul, Turkey
  21. 21NeuroCure Clinical Research Center (NCRC), Charité Universitätsmedizin Berlin, Berlin, Germany
  22. 22Medical Faculty, Department of Neurology, Heinrich–Heine–University Düsseldorf, Düsseldorf, Germany
  23. 23Molecular Neuroimmunology Group, Department of Neurology, University of Heidelberg, Germany
  24. 24Department of Clinical Medicine, University of Bergen, Bergen, Norway
  25. 25Department of Neurology, Haukeland University Hospital, Bergen, Norway
  26. 26Faculty of Medecine RTH Laennec, Lyon Neurosciences Research Centre, Neuro–inflammation and Neuro–oncology Team, Lyon, France
  27. 27Department of Neurology, University Hospital of Schleswig-Holstein, Campus Lübeck, Lübeck, Germany
  28. 28Institute for Quality Assurance, Lübeck, Germany
  1. Correspondence to Dr Patrick Waters, Nuffield Department of Clinical Neurosciences, Level 5/6 West wing, John Radcliffe Hospital, Headley Way, Oxford OX3 9DU, UK; paddy.waters{at}ndcn.ox.ac.uk

Abstract

Objective Antibodies to cell surface central nervous system proteins help to diagnose conditions which often respond to immunotherapies. The assessment of antibody assays needs to reflect their clinical utility. We report the results of a multicentre study of aquaporin (AQP) 4 antibody (AQP4-Ab) assays in neuromyelitis optica spectrum disorders (NMOSD).

Methods Coded samples from patients with neuromyelitis optica (NMO) or NMOSD (101) and controls (92) were tested at 15 European diagnostic centres using 21 assays including live (n=3) or fixed cell-based assays (n=10), flow cytometry (n=4), immunohistochemistry (n=3) and ELISA (n=1).

Results Results of tests on 92 controls identified 12assays as highly specific (0–1 false-positive results). 32 samples from 50 (64%) NMO sera and 34 from 51 (67%) NMOSD sera were positive on at least two of the 12 highly specific assays, leaving 35 patients with seronegative NMO/spectrum disorder (SD). On the basis of a combination of clinical phenotype and the highly specific assays, 66 AQP4-Ab seropositive samples were used to establish the sensitivities (51.5–100%) of all 21 assays. The specificities (85.8–100%) were based on 92 control samples and 35 seronegative NMO/SD patient samples.

Conclusions The cell-based assays were most sensitive and specific overall, but immunohistochemistry or flow cytometry could be equally accurate in specialist centres. Since patients with AQP4-Ab negative NMO/SD require different management, the use of both appropriate control samples and defined seronegative NMOSD samples is essential to evaluate these assays in a clinically meaningful way. The process described here can be applied to the evaluation of other antibody assays in the newly evolving field of autoimmune neurology.

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