A comparative study of antibody titers of blister fluid and serum in patients with subepidermal immunobullous diseases

BACKGROUND: Subepidermal autoimmune bullous diseases (SABD) comprise several disorders, such as bullous pemphigoid (BP), cicatricial pemphigoid (CP), epidermolysis bullosa acquisita (EBA), herpes gestationis (HG), and linear immunoglobulin A (IgA) dermatosis (LAD), and are characterized by antibody production against the basement membrane structures of the skin and mucosa. Although indirect immunofluorescence (IIF) on serum is a routine test for the detection of basement membrane zone antibodies, there have only been a few studies related to IIF on blister fluid. Aim To perform IIF on blister fluid and to compare the results with those of serum. METHODS: IIF on salt-split skin was performed on the serum and blister fluid of 35 patients with SABD (25 bp, three EBA, three HG, three LAD, and one bullous systemic lupus erythematosus) with conjugated IgG, IgA, and C3. RESULTS: Twenty-eight of the 35 patients showed IIF-positive blister fluid with a titer similar or less than that of serum. In 25 patients with BP, the most common disease in this study, 23 cases (92%) had positive IIF on serum, 23 cases (92%) on blister fluid, and 24 cases (96%) on either serum or blister fluid. Immunoreactant titers in BP blister fluid and serum did not show significant differences (P > 0.05). Epidermal binding of immunoreactants was the most prevalent staining pattern of IIF on salt-split skin (92%) in BP. CONCLUSIONS: From the findings of this study, the blister fluid of patients with SABD can be used for IIF. Although IIF sensitivity on blister fluid is no more than that on serum, the performance of this test on blister fluid in addition to serum may reduce the number of false negative results of IIF found using either of these two substrates alone.