Novel assay for detecting celiac disease-associated autoantibodies in dermatitis herpetiformis using deamidated gliadin-analogous fusion peptides

Background: Dermatitis herpetiformis (DH) is a cutaneous manifestation of celiac disease (CD), the latter being identified by circulating autoantibodies against native gliadin (nGli), tissue transglutaminase (tTG), endomysium, or a combination of these. Recently, a novel serologic assay using deamidated gliadin-analogous fusion peptides (GAF3X) showed high diagnostic sensitivity in patients with CD. Objective: The aim of this study was to explore the anti-GAF3X enzyme-linked immunosorbent assay (ELISA) and to compare it with a panel of classic CD-related serologic tests in patients with DH. Methods: Antibodies against nGli, GAF3X, and tTG were determined by separate ELISA tests and against endomysium by indirect immunofluorescence microscopy in 45 patients with DH and 52 control patients (30 patients with bullous pemphigoid and 22 patients with linear IgA disease). A total of 24 patients with DH underwent intestinal biopsies to confirm underlying CD. Results: Antibodies to nGli were detected in 26 (58%) (IgA) and 24 (53%) (IgG), to GAF3X in 38 (84%) (IgA) and 36 (80%) (IgG), to tTG in 35 (78%) (IgA), and to endomysium in 32 (71%) (IgA) patients with DH. Combined testing of IgA and IgG antibodies to GAF3X detected 7 of 10 (70%) IgA-anti-tTG-negative patients with DH and together with the IgA-anti-tTG ELISA showed the highest serologic hit rate (93%) for CD. Limitations: Intestinal biopsies were not performed in all patients with DH. Conclusion: The novel anti-GAF3X ELISA shows a higher sensitivity to detect CD-associated autoantibodies in patients with DH compared with tests using nGli, tTG, or endomysium as substrates.