Serological diagnostics in the detection of IgG autoantibodies against human collagen VII in epidermolysis bullosa acquisita – a multicenter analysis

Summary

Background

Epidermolysis bullosa acquisita is a rare, potentially devastating autoimmune disease of the skin. IgG autoantibodies directed against type VII collagen (Col7), the major component of anchoring fibrils, induce skin fragility leading to cutaneous and mucocutaneous blister formation which is mostly of a scaring phenotype. Thus, powerful and reproducible diagnostic assays are critical to establish the diagnosis of EBA early to avoid irreversible sequelae.

Objectives

The present international, retrospective multicenter study includes a large cohort of EBA patients and evaluated the diagnostic power of four different diagnostic assays for the detection of anti-Col7 IgG autoantibodies.

Methods

95 EBA sera and 200 control sera consisting of 100 bullous pemphigoid sera, 50 pemphigus vulgaris sera and 50 sera of healthy controls were tested for anti-Col7 IgG autoantibodies by indirect immunofluorescence (IIF), two commercial ELISA systems and Western blot (WB) analysis. EBA sera were from patients with positive DIF and IgG reactivity in at least one of the immune serological assays (IIF, ELISA, WB).

Results

A Col7-NC1/NC2 ELISA (MBL, Japan) showed the highest sensitivity (97.9%), followed by a Col7-NC1 ELISA (Euroimmun, Germany; 89.5%), WB with Col7-NC1 (85.3%), and IIF on saline split human skin (74.7%). The specificities of both ELISA systems were comparable (NC1: 98.7%, NC1/NC2: 99.3%). Furthermore, WB was more sensitive than IIF which was more specific.

Conclusions

The two commercially available ELISA systems allow for a highly sensitive and specific diagnosis of EBA. The sensitivity of the Col7-NC1/NC2 ELISA is significantly higher compared to the ELISA which is based on the Col7-NC1-domain only.

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