B-081 Analytical comparison of a novel, fully automated multiplexed microarray immunoassay and routine methods for the detection of IgA antibodies to tissue transglutaminase in a laboratory in England

Abstract Background Detection of autoantibodies directed to tissue transglutaminase (tTG) and deamidated gliadin peptide (DGP) is important in the assessment of individuals under clinical suspicion of celiac disease (CD). In this study, we compared the analytical performance for the detection of autoantibodies to tTG (IgA isotype), of the MosaiQ AiPlex® CD microarray (AiPlex CD. AliveDx, Switzerland), a CE-marked, novel, single-use, fully automated, multiplexed microarray immunoassay and routine methods. Methods De-identified serum samples, characterized as reactive or non-reactive for tTG IgA as per the routine practice method of the evaluation site (EliA™ Celikey® IgA, Phadia AB, Sweden), were tested with the evaluated device. Although AiPlex CD features the semi-quantitative measurement of both tTG IgA and IgG and anti-deamidated gliadin peptide (DGP) IgA and IgG antibodies, and qualitative measurement of total IgA in serum; this comparison was limited to tTG IgA as no samples characterized for other CD autoantibodies were available. Positive percent agreement (PPA) and negative percent agreement (NPA) were calculated. Double-sided 95% Confidence Intervals (CI) were calculated using Clopper-Pearson Exact Method. Results 77 samples characterized as reactive for tTG IgA by the routine method and 90 samples characterized as non-reactive for this marker were included in the analysis. The evaluated device identified 73 out of 77 samples characterized as reactive by the routine method, for a PPA of 95% (95% CI: 87.2, 98.5). Out of the four discordant samples, one also yielded a non-reactive result for tTG IgG and reactive results for both DGP IgA and IgG in the evaluated device and negative anti-endomysial antibodies (EMA) by immunofluorescence; two samples were reactive to DGP IgA or DGP IgG by the evaluated device and one sample was non-reactive to all four markers and was negative to EMA. Regarding the samples characterized as non-reactive by the routine method, the evaluated device identified 86 out of 90, for an NPA of 96% (95% CI: 89.0, 98.7). For the four samples with discordant results, the evaluated device also yielded reactive results for at least one additional CD antibody (tTG IgG, DGP IgA, DGP IgG). Conclusion In this study, the AiPlex CTD diagnostic system showed high concordance with the compared routine method for the serological assessment of tTG IgA, a key marker in the evaluation of CD.