Enzyme-linked immunosorbent assay in autoimmune blistering diseases: preliminary experience of the Dermatology Department of Cagliari.

AIM: Recent insights on the pathogenesis of autoimmune blistering diseases have pointed out the opportunity of new diagnostic tools, such as enzyme-linked immunosorbent assay (ELISA) for Desmogleins 3 and 1 (Dsg3, Dsg1), and bullous pemphigoid (BP) 180 antigen auto-antibodies. The aim of the present prospective study was to evaluate the diagnostic values of these tests in blind with histopathology and direct immunofluorescence (DIF), the assessment of correlation with clinical presentation and severity of disease, as well as eventual modifications of serum auto-antibodies titres in course of treatment.

METHODS: From June 2005 to June 2007, all consecutive patients with clinically blistering diseases presenting to the Dermatology Department of Cagliari were enrolled in the study. Biopsy specimens were performed in all cases and sent for histopathological examinations including haematoxylin-eosin stain and DIF to the Unit of Pathological Anatomy of the same University. Serum samples were tested with Dsg3, Dsg1 and BP180 ELISA in the internal laboratory of the Dermatology Department, and results were worked out many days before histopathology reports. Final diagnosis was established on clinical, histological and immunopathological findings. A selected sample of patients with active autoimmune blistering disease underwent repeated immunosorbent assays at 1-2-6 months from first diagnosis and treatment introduction.

RESULTS: Forty-two patients (23 men, 19 women) were enrolled in the study and divided into three groups: pemphigus (N=17), pemphigoid (N=19) and other diseases (OD; N=6), depending on the final diagnosis assessed by histological, immunopathological and serological examinations. In pemphigus group ELISA showed circulating antibodies against Dsg3 in all patients (100%) and against Dsg1 in 13 patients (76.5%). In the pemphigoid group, 16 of 19 sera showed positive scores above the cut-off value (84.2%), but sensibility was higher if considering only the bullous pemphigoid final diagnosis (16/17). None of the other bullous diseases (0%) exceeded the cut-off value for Dsg1, Dsg3 and BP180 ELISA. Correlation with histopathology and direct immunofluorescence was excellent for pemphigus and very good for pemphigoid. Eight patients (6 P; 2 BP) underwent a serial measurement of the autoantibodies levels: two patients (1 PV and 1 BP) showed an ELISA antibodies titres decrease after two months of treatment, in parallel with an excellent clinical response. Whereas in six cases (5 PV and 1 BP) the ELISA titres overstayed high at I and II month. Clinically the disease was active in all six patients, and a treatment adjustment was performed (increased corticosteroid dosage and/or azathioprine initiation in all cases, high dose intravenous immune globulin in one case). At month VI, a decrease on ELISA antibody levels was documented in three patients (3 PV), parallel to a clinical remission. Whereas in other three patients (2 PV, 1 BP), persistent high Dsg3 ELISA titres were related to a still active disease: although clinically improved, blisters flared up at any attempt to taper drugs dosage.

CONCLUSION: Dsg3, Dsg1 and BP ELISA is a sensitive, easy and quick reading tool for the diagnosis of the main autoimmune blistering diseases: pemphigus and bullous pemphigoid. More over, autoantibodies titre correlate with disease severity, and is useful to monitor treatment response.