Comparison of 3 type VII collagen (C7) assays for serologic diagnosis of epidermolysis bullosa acquisita (EBA)

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-length–C7 ELISA developed in our laboratory. Methods C7-NC1/NC2 ELISA, IIFT, and full-length–C7 ELISA were run on 77 nonselected consecutive EBA sera. Results C7-NC1/NC2 ELISA, IIFT, and full-length–C7 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 + ); 9%, 22%, and 47% of 32 SSS/F − 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 + and SSS/F − sera, and IIFT versus full-length–C7 ELISA. Limitations The retrospective design was a limitation. Conclusion C7-NC1/NC2 ELISA and IIFT sensitivities for serologic diagnoses of EBA were low. Full-length–C7 ELISA was significantly more sensitive and could serve as a reference test.