AUTHOR=Pandit Lekha , D’Cunha Anitha , Malli Chaithra , Sudhir Akshatha 

TITLE=Comparison of live and fixed cell-based assay performance: implications for the diagnosis of MOGAD in a low-middle income country

JOURNAL=Frontiers in Immunology

VOLUME=Volume 14 - 2023

YEAR=2023

URL=https://www.frontiersin.org/journals/immunology/articles/10.3389/fimmu.2023.1252650

DOI=10.3389/fimmu.2023.1252650

ISSN=1664-3224

ABSTRACT=Background: Live CBA is often unavailable for the diagnosis of MOGAD in resource poor regions. This study was undertaken to determine the agreement between live CBA (LCBA) and the widely available fixed cell based assay (FCBA), for recommending testing guidelines within our region. 
Method: All consecutive patients in our registry having a MOGAD phenotype were tested.  The results from a commercially available FCBA (Euroimmun, Germany) were compared with a validated live “in house” CBA. Clinical and MRI data was available for correlation.
Results: Among 257 patient samples tested, 118 (45.9%) were positive by FCBA titre ≥1: 10 and or LCBA titres ≥1: 160 titre and 139 samples were negative. There was robust agreement between the two assays (agreement 98.8%, Cohen’s kappa 0.98 [95% CI- 0.95-1.00], Spearman correlation 0.97 (p < 0.0001). Among 5 discordant samples, four had clinical and or MRI data which supported an alternate diagnosis. There was a modest correlation between assay titres, particularly for samples with titres ≥ 1:100 in FCBA (Spearman’s Rho 0.26, p 0.005). Thirty samples were positive by FCBA at < 1:100 titre and included 1:80 (20),1:40(7) and 1:10 (3) titres. Among them, 80% had clear positive titres when tested by LCBA.
Conclusion: The FCBA tested in serum dilutions of 1:10 was highly predictive of MOGAD in our study and compared well with our “in house” LCBA. The current recommendations for testing at higher dilutions need to be re-examined, in the light of our findings. The results of our study should ideally be replicated in a larger data set, but at the same time provides some guidance for the accurate diagnosis of MOGAD in resource poor settings.