ORIGINAL ARTICLE Comparison of 3 type VII collagen (C7) assays for serologic diagnosis of epidermolysis bullosa acquisita (EBA) Vannina Seta, a Franc ¸oise Aucouturier, PhD, b Jonathan Bonnefoy, PhD, c,d Christelle Le Roux-Villet, MD, a Val erie Pendaries, PhD, e Marina Alexandre, MD, a Sabine Grootenboer-Mignot, MD, PhD, f Michel Heller, PhD, g Nicole Li evre, g Liliane Laroche, MD, PhD, a Fr ed eric Caux, MD, PhD, a Matthias Titeux, PhD, c,d Alain Hovnanian, MD, PhD, c,d,h and Catherine Prost-Squarcioni, MD, PhD a,g,i Bobigny, Paris, and Toulouse, France Background: Serologic diagnosis of epidermolysis bullosa acquisita (EBA) relies on the detection of circulating autoantibodies to type VII collagen (C7). Objective: We sought to compare the diagnostic performances of a commercialized enzyme-linked immunosorbent assay (ELISA) using C7 noncollagenous (NC) domains (C7-NC1/NC2 ELISA) and indirect immunofluorescence (IIF) biochip test on NC1-C7-expressing transfected cells (IIFT), with a full-lengtheC7 ELISA developed in our laboratory. Methods: C7-NC1/NC2 ELISA, IIFT, and full-lengtheC7 ELISA were run on 77 nonselected consecutive EBA sera. Results: C7-NC1/NC2 ELISA, IIFT, and full-lengtheC7 ELISA were positive, respectively, for: 30%, 27%, and 65% of the 77 sera; 43%, 32%, and 80% of 44 sera labeling the salt-split-skin (SSS) floor (F) by IIF (SSS/F 1 ); 9%, 22%, and 47% of 32 SSS/F À sera; 28%, 28%, and 58% of classic EBA; 41%, 41%, and 82% of inflammatory EBA; and 18%, 0%, and 55% of mucous-membrane-predominant EBA. Significant differences for all sera were found between: the 2 ELISAs for the 77 sera, SSS/F 1 and SSS/F À sera, and IIFT versus full-lengtheC7 ELISA. Limitations: The retrospective design was a limitation. Conclusion: C7-NC1/NC2 ELISA and IIFT sensitivities for serologic diagnoses of EBA were low. Full-lengtheC7 ELISA was significantly more sensitive and could serve as a reference test. ( J Am Acad Dermatol http://dx.doi.org/10.1016/j.jaad.2016.01.005.) Key words: autoimmune bullous disease; biochip; enzyme-linked immunosorbent assay; epidermolysis bullosa acquisita; indirect immunofluorescence; sensitivity; serologic diagnosis; type VII collagen. E pidermolysis bullosa acquisita (EBA) is a sub- epithelial autoimmune bullous disease (AIBD) characterized by anti-type VII collagen (C7) autoantibodies bound in vivo to the anchoring fibrils of the basement membrane zone. 1 Clinically, EBA can have a classic mechanobullous phenotype (classic EBA From the Departments of Dermatology a and Pathology, i APHP, Avicenne Hospital, Bobigny; Department of Immunology, Assis- tance Publique des H^ opitaux de Paris (APHP), Saint-Louis Hos- pital, Paris b ; Institut National de la Sant e et de la Recherche M edicale (INSERM), Unit e Mixte de Recherche (UMR) 1163, Institut Imagine, Paris c ; Universit e Paris DescarteseSorbonne Paris Cit e d ; INSERM, U563, Purpan Hospital, Toulouse e ; Depart- ment of Immunology, APHP, Bichat Hospital, Paris f ; Department of Histology, Unit e de Formation et de Recherche (UFR) L eonard de Vinci, University Paris 13, Bobigny g ; and Department of Genetics, APHP, NeckereEnfants Malades Hospital, Paris. h Drs Prost-Squarcioni and Hovnanian have equally contributed to this work and share last authorship. Supported by GENEGRAFT FP17 European Project and Dystrophic Epidermolysis Bullosa Research AssociationeFrance. Conflicts of interest: None declared. Presented as an oral e-poster at the 24th European Academy of Dermatology and Venereology Congress in Copenhagen, Denmark, October 7-11, 2015. Accepted for publication January 1, 2016. Reprint requests: Catherine Prost-Squarcioni, MD, PhD, Department of Dermatology, APHP, Avicenne Hospital, 125, route de Stalingrad, 93009 Bobigny Cedex, France. E-mail: catherine. prost@aphp.fr. Published online March 3, 2016. 0190-9622/$36.00 Ó 2016 by the American Academy of Dermatology, Inc. http://dx.doi.org/10.1016/j.jaad.2016.01.005 1