Evaluation of BP180 and BP230 ELISA in the diagnosis of mucous membrane pemphigoid limited to the oral cavity: preliminary results

Objectives. Mucous Membrane Pemphigoid (MMP) is the clinical phenotype of a group of rare autoimmune blistering diseases characterized by autoantibodies directed against different structural proteins in epithelial basement membranes. Diagnoses of MMP is routinely verified by direct immunofluorescence (DIF) of oral mucosa biopsy tissue. ELISA detection of autoantibodies in serum is now employed for the diagnosis of pemphigoid and for monitoring the disease activity. The aim of this study was to evaluate ELISA sensitivity, specificity, PPV, NPV in oral MMP patients. Methods. Patients with oral lesions compatible with MMP, were enrolled. Two different specimens were obtained during the surgical biopsy: one for the histopathological assessment and the other for the DIF. ELISA plates, precoated with recombinant ectodomains of the epitope NC16a of the BP180 antigen and carboxy-terminal domains of BP230 antigen were used. All ELISAs were performed according to the manufacturer’s instructions. Values greater than 8,7 U/ml were considered positive. Histopathological and DIF results were considered as the gold standard. Global validation of the test results was established by calculating the sensitivity, specificity and both the positive and negative predictive values. Results. Sixty-four patients were enrolled (M:F=1:4). Ages ranged from 40 to 82 years (mean 61 years). There were 30 patients with MMP, 16 patients with OLP, 14 affected by PV, 3 lichenoid dysplasia and 1 erythema multiforme. ELISA sensitivity and specificity was respectively 47 and 79%. PPV percentage was 67% while NPV was 63%. Conclusions. In suspected oral MPP, both ELISA tests and histopathological + DIF have to be performed because of ELISA low sensitivity. Although BP180 and BP230 are the major target antigens in patients with MMP limited to the oral cavity, they are not the only. This aspect may explain the low sensitivity rate of ELISA in oral MMP when used as the sole diagnostic support