Testing for Neuromyelitis Optica Due to Aquaporin-4 Antibodies

The gold standard for diagnosing immunoglobulin G aquaporin-4–positive (AQP4+) neuromyelitis optica spectrum disorder (NMOSD) is use of a cell-based assay (CBA), but this option requires specialized equipment that is not available everywhere. Researchers in China and Korea have now tested a simpler, investigational (not U.S. FDA-approved) rapid enzyme immunodot assay (RIA). For this case-control study, a total of 836 serum samples were collected, with 400 used in the diagnostic study and 436 in two separate validation studies.

Of the total, 40% were AQP4 positive by CBA. Compared with the CBA, the RIA was 99.4% sensitive and 99.2% specific. The RIA had 2 false-negative tests out of 332 and 4 false-positive tests out of 504.