A practical alternative to live cell-based assay for AQP4 and MOG antibody detection

Background Live cell-based assay (LCBA) is the gold standard for sensitive detection of aquaporin-4 (AQP4) and myelin oligodendrocyte glycoprotein (MOG) autoantibodies in neuromyelitis optica spectrum disorder (NMOSD) and MOG antibody-associated disorder (MOGAD). However, LCBA is less practical, standardisable and cost-effective than fixed cell-based assay (FCBA). Methods We developed a high-performance untransfected vector cells lysate, named AbFine, to process patients' sera to pre-bind and deplete interferents before FCBA, and examined its rationality. We then conducted a multicentre, double-blind, prospective discovery study to compare the diagnostic accuracy of conventional FCBA, FCBA-AbFine, and LCBA in detecting AQP4-IgG and MOG-IgG. A retrospective validation cohort was used to assess generalisability. Participants included patients with NMOSD, MOGAD, and seronegative inflammatory demyelination syndromes, and controls with other neurological disorders. Findings 818 participants were recruited, including 410 in the discovery and 408 in the validation cohorts with good consistency. Among 205 patients with NMOSD, AQP4-IgG was detected in 165, 185, and 178 by FCBA, FCBA-AbFine, and LCBA, yielding sensitivity of 80.5% (95% CI, 74.4–85.7), 90.2% (95% CI, 85.3–93.9), and 86.8% (95% CI, 81.4–91.1), respectively. Among 171 patients with MOGAD, MOG-IgG was found in 134, 155, and 158 by FCBA, FCBA-AbFine, and LCBA, with sensitivity of 78.4% (95% CI, 71.4–84.3), 90.6% (95% CI, 85.3–94.6), and 92.4% (95% CI, 87.4–95.9), respectively. All assays achieved specificity greater than 99.5%. The area under the curve for FCBA-AbFine was higher than that for FCBA for both AQP4-IgG (0.950 vs. 0.902; p < 0.0001) and MOG-IgG (0.935 vs. 0.888; p < 0.05), and was comparable to LCBA (AQP4-IgG 0.950 vs. 0.934; MOG-IgG 0.935 vs. 0.940; p > 0.05 for both). Interpretation AbFine enables the use of FCBA as an alternative to LCBA in AQP4-IgG and MOG-IgG detection with operationally practical and cost-efficient characteristics and could be extended to other fixed cellular assays. Funding Beijing Precigen Biopharma Co., Ltd., Beijing, China.