Objectives: To compare the reproducibility of 11 antibody assays for IgG and IgM myelin oligodendrocyte glycoprotein antibodies (MOG-IgG, MOG-IgM) from five international centers.
Methods: The following samples were analyzed: MOG-IgG clearly positive sera (n=39), MOG-IgG low positive sera (n=39), borderline negative sera (n=13), clearly negative sera (n=40), and healthy blood donors (n=30). As technical controls, 18 replicates (9 MOG-IgG positive and 9 negative) were included. All samples and controls were re-coded, aliquoted, and distributed to the five testing centers which performed the following antibody assays: five live and one fixed immunofluorescence cell-based assays (CBA-IF, five MOG-IgG, one MOG-IgM), three live flow cytometry cell-based assays (FACS-CBA, all MOG-IgG), and two enzyme-linked immunosorbent assays (ELISA, both MOG-IgG).
Results: We found excellent agreement (96%) between the live CBAs for MOG-IgG for samples previously identified as clearly positive or negative from four different national testing centers. The agreement was lower with fixed CBA-IF (90%) and the ELISA showed no concordance with CBAs for detection of human MOG-IgG. All CBAs showed excellent inter-assay reproducibility. The agreement of MOG-IgG CBAs for borderline negative (77%) and particularly low positive (33%) samples was less good. Finally, most samples from healthy blood donors (97%) were negative for MOG-IgG in all CBAs.
Conclusion: Live MOG-IgG CBAs showed excellent agreement for high positive and very good agreement for negative samples at four international testing centers. Low positive samples were more frequently discordant than in similar assays for other autoantigens. Further research is needed to improve international standardization for clinical care.