Rapid Immunodot AQP4 Assay for Neuromyelitis Optica Spectrum Disorder

Abstract

ImportanceImmunoglobulin G autoantibodies for aquaporin 4 (AQP4-IgG) serve as diagnostic biomarkers for neuromyelitis optica spectrum disorder (NMOSD), and the most sensitive and specific laboratory tests for their detection are cell-based assays (CBAs). Nevertheless, the limited availability of special instruments limits the widespread use of CBAs in routine laboratories.ObjectiveTo validate an enzyme immunodot assay for simple and rapid detection of AQP4-IgG.Design, Setting, and ParticipantsThis multicenter case-control study, conducted from May 2020 to February 2023, involved 4 medical centers (3 in China and 1 in Korea). The study included patients with AQP4-IgG–positive NMOSD, patients with other immune-related diseases, and healthy control individuals. Participants were excluded if they did not agree to participate or if their serum sample had turbidity.ExposuresSerum AQP4 antibodies measured with immunodot assay.Main Outcomes and MeasuresThe main outcome was performance of the immunodot assay compared with the gold standard CBA for detecting AQP4-IgG. To examine generalizability, cross-validation in Korea and at a second site in China, validation of patients with other immune-related diseases, and follow-up validation of the original cohort were performed.ResultsA total of 836 serum samples were collected; 400 were included in the diagnostic study and 436 in the validation sets. In a head-to-head diagnostic study involving 200 patients with NMOSD with AQP4-IgG (mean [SD] age, 43.1 [13.5] years; 188 [94%] female) and 200 healthy controls, use of an immunodot assay demonstrated antibody detection performance comparable to that of the gold standard (κ = 98.0%). The validation sets included 47 patients with NMOSD and 26 patients with other autoimmune diseases from Korea, 31 patients with NMOSD at a second site in China, 275 patients with other diseases, and 57 patients with NMOSD at follow-up. In the validation study, of 436 cases, 2 (<1%) were false positive and none were false negative. The CBA identified 332 AQP4-IgG–positive samples and 504 negative samples (200 [40%] in controls and 304 [60%] in patients with other diseases); 2 of the positive cases (<1%) were false negative and 4 of the negative cases (<1%) were false positive. The overall sensitivity of the immunodot assay was 99.4% (95% CI, 97.8%-99.9%), and the specificity was 99.2% (95% CI, 98.0%-99.8%).Conclusions and RelevanceThis case-control study found that the immunodot assay was comparable to CBA for detecting AQP4-IgG. With its time- and cost-efficient characteristics, the immunodot assay may be a practical option for AQP4-IgG detection.

The relationship between serum astroglial and neuronal markers and AQP4 and MOG autoantibodies

“…The clear separation of the patient groups is crucial, since inappropriate treatments following a false diagnosis may exacerbate symptoms (11,(26)(27)(28). With current assays showing low sensitivity for αAQP4 (29) and being dependent on treatment and clinical status (30,31), and better, newer assays not being used in the clinic as of yet (32), strong interrelated differentiators should be useful.…”

Integrative analysis of purine metabolites and gut microbiota in patients with neuromyelitis optica spectrum disorders after mycophenolate mofetil treatment

“…Neuromyelitis optica spectrum disorders (NMOSD) is a severe, disabling autoimmune disease of the central nervous system (CNS) characterized by its association with serum anti-aquaporin-4 antibodies (AQP4-IgG) [1][2][3][4]. Clinically, NMOSD results in a range of syndromes of varied severities including recurrent paralysis, blindness and brain syndromes [5].…”

Discussion on the Application of Rapid Immunoblot Assay for AQP4-IgG Detection—Reply

“…In Reply We thank Su and Wang for their valuable insights of our recent article on the rapid immunodot aquaporin 4 (AQP4) assay for neuromyelitis optica spectrum disorder (NMOSD).…”