Detection of Anti‐Aquaporin‐4 Antibodies in Neuromyelitis Optica: Comparison of Tissue‐Based and Cell‐Based Indirect Immunofluorescence Assays and ELISA

NMO ‐ I g G against aquaporin‐4 ( AQP 4) is a specific marker for neuromyelitis optica ( NMO ). We evaluated the performance of different NMO ‐ I g G detecting methods. In 124 sera (from 54 with NMO spectrum disorders including nine with NMO , ten with multiple sclerosis including two with OSMS , and 60 with other neurological diseases), NMO ‐ I g G was measured with tissue‐based indirect immunofluorescence ( IIF ‐tissue) using mouse cerebellum, cell‐based IIF ( IIF ‐ AQP 4) using transfected HEK 293 cells which express human AQP 4, and AQP 4 autoantibody detecting enzyme linked immunosorbent assay ( ELISA ‐ AQP 4). The sensitivities and specificities of three assays were 44.4–55.6% and 87.0–92.2% for detecting NMO , and 11.1–20.4% and 95.7–97.1% for detecting NMO spectrum disorders. Although there was no significant difference, the patients with NMO or NMO spectrum disorders showed higher rates of seropositivity in the ELISA ‐ AQP 4 vs. IIF assays. Out of the 19 sera with NMO ‐ I g G , in at least one test, only six (31.6%) were found to be positive by all three assays. Among the three methods, the ranges of co‐negativities, co‐positivities, and agreement were 77.4–97.4%, 42.9–75.0%, and 91.1–95.2% (kappa 0.475–0.641), respectively. In patients who had positive ELISA ‐ AQP 4 results, IIF ‐ AQP 4 positivity was associated with NMO ( P = 0.01). In summary, we observed an increased prevalence of NMO ‐ I g G in patients with NMO and NMO spectrum disorders. ELISA ‐ AQP 4 may be more sensitive and specific when confirmed by IIF ‐ AQP 4. J. Clin. Lab. Anal. 26:184‐189, 2012. © 2012 Wiley Periodicals, Inc.