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A new M23-based ELISA assay for anti-aquaporin 4 autoantibodies: diagnostic accuracy and clinical correlation

  • Tampoia, Marilina1
  • Abbracciavento, Letizia1
  • Barberio, Giuseppina2
  • Fabris, Martina3
  • Bizzaro, Nicola4
  • 1 University of Bari, Clinical Pathology Laboratory, Polyclinic of Bari, Department of Biomedical Sciences and Human Oncology, Piazza Giulio Cesare 11, Bari, 70124, Italy , Bari (Italy)
  • 2 Treviso Hospital, Laboratory Medicine, Department of Clinical Pathology, Treviso, Italy , Treviso (Italy)
  • 3 University Hospital Udine, Laboratory of Immunopathology and Allergology, P.le S. Maria della Misericordia 15, Udine, 33100, Italy , Udine (Italy)
  • 4 Azienda Sanitaria Universitaria Integrata di Udine, Laboratory of Clinical Pathology, San Antonio Hospital, Udine, Italy , Udine (Italy)
Published Article
Autoimmunity Highlights
BioMed Central
Publication Date
Jun 19, 2019
DOI: 10.1186/s13317-019-0115-7
Springer Nature


PurposeAlthough many assays have been developed to detect anti-aquaporin-4 (AQP4) antibodies, most of these assays require sophisticated techniques and are thus only available at specialized laboratories. The aim of this study was to evaluate the analytical and clinical performance of a new commercial enzyme-linked immunosorbent assay (ELISA RSR, AQP4 Ab Version 2) to detect anti-AQP4 antibodies performed on a fully automated system (SkyLAB 752).MethodsSerum samples from 64 patients with neuromyelitis optica spectrum disorders (NMOSD) (including NMO, longitudinally extensive myelitis-LETM, optical neuritis and myelitis) and 27 controls were tested for anti-AQP4 antibodies. All sera were previously tested using an indirect immunofluorescence (IIF) method on primate tissue, as the reference method. Commercial control sera were used to determine within-run, between-day and within-laboratory precision (CLSI guidelines).ResultsAt a cut-off value of 2.1 U/mL as determined by ROC curves, sensitivity and specificity for NMO were 83.3% and 100%, respectively. The ELISA assay provided 100% concordant results with the reference IIF method. The median concentration of anti-AQP4 antibodies was statistically higher in patients with NMO than in patients with LETM (p = 0.0006) or with other NMOSD and in controls (p < 0.0001). At the concentration of 12.4 and 28.1 U/mL, the within-run, between-day and within-laboratory coefficients of variation (CV) were 3.2% and 3%, 7.6% and 7.4%, and 8.2% and 8.0%, respectively.ConclusionsThis new ELISA method performed on a fully automated system, showed high sensitivity and absolute specificity, good CV in precision tests, and provided observer-independent quantitative results.

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