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Updated: Apr 21, 2026
Human Serum Anti-aquaporin-4 Immunoglobulin G Detection by Cell-based Assay
Published on: April 5, 2019
AQP4 autoantibody assay performance in clinical laboratory service
J P Fryer1, V A Lennon1, S J Pittock1
1Departments of Laboratory Medicine and Pathology (J.P.F., V.A.L., S.J.P., E.H., E.A.J., A.M.), Neurology (V.A.L., S.J.P., S.L.C., C.F.L., B.G.W., A.M.), Immunology (V.A.L.), and Health Sciences Research (S.M.J.), College of Medicine, Mayo Clinic, Rochester, MN; Institute of Pathology and Neuropathology (P. F.-B.), University of Tubingen, Germany; Department of Neurology (E.A.S.), College of Medicine, Mayo Clinic, Jacksonville, FL; and Department of Neurology (D.M.W.), College of Medicine, Mayo Clinic, Scottsdale, AZ.
Objective:
To compare performance of contemporary aquaporin-4-immunoglobulin (Ig) G assays in clinical service.
Methods:
Sera from neurologic patients (4 groups) and controls were tested initially by service ELISA (recombinant human aquaporin-4, M1 isoform) and then by cell-based fluorescence assays: fixed (CBA, M1-aquaporin-4, observer-scored) and live (fluorescence-activated cell sorting [FACS], M1 and M23 aquaporin-4 isoforms). Group 1: all Mayo Clinic patients tested from January to May 2012; group 2: consecutive aquaporin-4-IgG-positive patients from September 2011 (Mayo and non-Mayo); group 3: suspected ELISA false-negatives from 2011 to 2013 (physician-reported, high likelihood of neuromyelitis optica spectrum disorders [NMOSDs] clinically); group 4: suspected ELISA false-positives (physician-reported, not NMOSD clinically).
Results:
Group 1 (n = 388): M1-FACS assay performed optimally (areas under the curves: M1 = 0.64; M23 = 0.57 [p = 0.02]). Group 2 (n = 30): NMOSD clinical diagnosis was confirmed by: M23-FACS, 24; M1-FACS, 23; M1-CBA, 20; and M1-ELISA, 18. Six results were suspected false-positive: M23-FACS, 2; M1-ELISA, 2; and M23-FACS, M1-FACS, and M1-CBA, 2. Group 3 (n = 31, suspected M1-ELISA false-negatives): results were positive for 5 sera: M1-FACS, 5; M23-FACS, 3; and M1-CBA, 2. Group 4 (n = 41, suspected M1-ELISA false-positives): all negative except 1 (positive only by M1-CBA). M1/M23-cotransfected cells expressing smaller membrane arrays of aquaporin-4 yielded fewer false- positive FACS results than M23-transfected cells.
Conclusion:
Aquaporin-4-transfected CBAs, particularly M1-FACS, perform optimally in aiding NMOSD serologic diagnosis. High-order arrays of M23-aquaporin-4 may yield false-positive results by binding IgG nonspecifically.
