Diagnosis And Disease Severity Assessment Of Epidermolysis Bullosa Acquisita By Elisa For Anti-Type Vii Collagen Autoantibodies : an Italian Multicenter Study

Background:  Epidermolysis bullosa acquisita (EBA) is a rare autoimmune mucocutaneous bullous disease caused by autoantibodies against type VII collagen, a component of anchoring fibrils which stabilizes the dermo-epidermal adherence. Type VII collagen is composed of a collagenous domain linked by non-collagenous NC1 and NC2 domains. Objective:  To assess the repeatability, sensitivity and specificity of a recently developed ELISA for detection of autoantibodies anti-type VII collagen and to ascertain whether it may be a marker of disease activity in EBA. Patients and Methods:  Using this ELISA able to recognize autoantibodies against NC1 and NC2 epitopes of type VII collagen, we tested 14 EBA sera, 30 healthy control sera and 113 disease control sera. Results:  Twelve out of the 14 EBA sera were positive in ELISA, with autoantibody titers varying from 7.2 to 127.9 U/ml (cut-off value: <6), the sensitivity of the method being of 85.7%. Among the controls, only two bullous pemphigoid sera resulted positive, the specificity being of 98.6%. A good correlation was found between EBA disease severity expressed as ABSIS score and the serum levels of anti-collagen VII autoantibodies measured by ELISA (n=14; r=0.965; p=0.0001). The intra- and inter-assay coefficients of variation of the ELISA method ranged from 6.3% to 18.3%. Conclusions:  This NC1 + NC2 ELISA can be a practical assay for the diagnosis of EBA. The correlation between autoantibody titers and disease severity suggests its usefulness as a marker of disease activity in EBA, which however should be confirmed by studies on larger series of patients.