Simultaneous detection of celiac disease-specific IgA antibodies and total IgA.

Purpose: Celiac disease (CD) serology requires analysis of tissue transglutaminase type-2 (TG2autoAbs), deamidated gliadin (DGAbs), and as reference endomysial autoantibodies (EmA). Total IgA assessment helps to determine IgA-deficient CD patients. The novel multiplex indirect immunofluorescence (IIF) technique CytoBead was used to develop the first quantitative one-step serological CD assay comprising both simultaneous IgA autoAb and total IgA testing.

Methods: CytoBead CeliAK detecting TG2autoAb, DGAb, EmA, and simultaneously total IgA uses fluorescent microparticles for antigen and antibody immobilization along with monkey-esophagus tissue sections on glass slides. The assay was interpreted visually by classical fluorescent microscopy and digital IIF using AKLIDES(®). Overall, 380 samples (155 CD patients, 5 with IgA deficiency, 68 with cystic fibrosis, 59 with eye disease, 93 blood donors) were run for performance analysis. Data were compared with classical IgA autoAb analysis by ELISA and IIF.

Results: Comparing CD-specific IgA autoAb testing by CytoBead with classical IIF and ELISA, very good agreements for EmA, TG2autoAb, and DGAb were determined (Cohen's κ = 0.98, 0.96, 0.85, respectively). The difference between multiplex and single testing revealed a significant difference for TG2autoAb testing only (McNemar, p = 0.0078). Four CD patients and 4 controls demonstrated TG2autoAb positivity by ELISA but were negative by CytoBead. Further, 140/155 (90.9 %) CD patients demonstrated TG2autoAb levels above ten times the upper normal and all five IgA-deficient samples IgA levels <0.2 g/L by CytoBead.

Conclusions: The novel multiplex CytoBead CeliAK enables simultaneous CD-specific autoAb and IgA deficiency analyses comparable with classical testing by single-parameter assays. Thus, comprehensive CD serology by CytoBead can alleviate the workload in routine laboratories.