Abstract Details

Title Frequency of Seroconversion in Aquaporin-4 Antibody Testing: Insights from Real-World Data

Topic Autoimmune Neurology

Presentation(s) P12 - Poster Session 12 (11:45 AM-12:45 PM)

Poster/Presentation
Number 8-001

Objective To assess the frequency of AQP4-IgG seroconversion across different testing methods in a large real-world clinical database.

Background Seroconversion of aquaporin-4 immunoglobulin G (AQP4-IgG) from negative to positive has been reported in a few cases. There is concern that seronegative neuromyelitis optica spectrum disorder (NMOSD) cases should be serially tested. Data from real-world clinical practice are needed to guide AQP4-IgG testing.

Design/Methods This retrospective clinical cohort included all patients with ≥2 AQP4-IgG tests, with the first test negative, between 2006-2024 by all methods (CBA (fixed and live), IFA, or ELISA). The frequency of seroconversion was evaluated.

Results 451 individuals with ≥2 AQP4-IgG tests with their first test negative were included. The mean age was 41 years (SD 15) and 330 (73%) were female. The median number of tests was 2 (range: 2–6), with a median follow-up period of 6.4 years (IQR: 3–10). Of the 451 individuals, the first negative test was CBA in 263 (58%), IFA in 170 (38%), ELISA in 4 (1%), and IFA plus ELISA in 14 (3%). Seroconversion of AQP4-IgG was identified in 8/451 individuals (1.8%) with NMOSD all first tested by IFA (8/170, 4.7%). Among the 8 seroconverters, 5 were subsequently positive by IFA, 2 by IFA plus ELISA and 1 by CBA. No seroconversions were observed among 263 with an initial negative CBA test.

Conclusions There were no cases of seroconversion in patients first tested by CBA methods suggesting repeat AQP4-IgG testing in patients initially negative by CBA has limited clinical value. All seroconversion cases occurred in patients first tested with IFA, likely reflective of the known low sensitivity of this method. Therefore, repeat testing may be useful in patients with a clinical diagnosis of NMOSD and early negative IFA test.

Authors/Disclosures
Tatchaporn Ongphichetmetha PRESENTER	Miss Ongphichetmetha has nothing to disclose.
Mengke Du (Cleveland Clinic)	Mengke Du has nothing to disclose.
Nisa Vorasoot, MD	Dr. Vorasoot has nothing to disclose.
Sean J. Pittock, MD, FAAN (Mayo Clinic Dept of Neurology)	Dr. Pittock has received personal compensation in the range of $500-$4,999 for serving as a Consultant for Arialys. The institution of Dr. Pittock has received personal compensation in the range of $5,000-$9,999 for serving on a Scientific Advisory or Data Safety Monitoring board for Alexion. The institution of Dr. Pittock has received personal compensation in the range of $500-$4,999 for serving on a Scientific Advisory or Data Safety Monitoring board for UCB. The institution of Dr. Pittock has received personal compensation in the range of $5,000-$9,999 for serving on a Scientific Advisory or Data Safety Monitoring board for Roche/Genentech. The institution of Dr. Pittock has received personal compensation in the range of $10,000-$49,999 for serving on a Speakers Bureau for Alexion/AstraZeneka. The institution of Dr. Pittock has received research support from NIH. Dr. Pittock has received intellectual property interests from a discovery or technology relating to health care. Dr. Pittock has received intellectual property interests from a discovery or technology relating to health care. Dr. Pittock has received publishing royalties from a publication relating to health care.
Jeffrey A. Cohen, MD (Cleveland Clinic)	Dr. Cohen has received personal compensation in the range of $10,000-$49,999 for serving as a Consultant for Convelo. Dr. Cohen has received personal compensation in the range of $500-$4,999 for serving as a Consultant for Astoria. Dr. Cohen has received personal compensation in the range of $5,000-$9,999 for serving as a Consultant for Bristol Myers Squibb. Dr. Cohen has received personal compensation in the range of $500-$4,999 for serving as a Consultant for Viatris. Dr. Cohen has received personal compensation in the range of $500-$4,999 for serving as a Consultant for PSI. Dr. Cohen has received personal compensation in the range of $500-$4,999 for serving as a Consultant for Shionogi. Dr. Cohen has received personal compensation in the range of $500-$4,999 for serving on a Scientific Advisory or Data Safety Monitoring board for Celltrion.
Amy Kunchok, MBBS (Cleveland Clinic - Mellen Centre)	Dr. Kunchok has received personal compensation in the range of $10,000-$49,999 for serving as an Editor, Associate Editor, or Editorial Advisory Board Member for Neurology:Open Access Journal .

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