Comparative study of indirect immunofluorescence and immunoblotting for the diagnosis of autoimmune pemphigus

The diagnosis of pemphigus relies on immunopathological criteria including the detection of circulating autoantibodies to desmosomal components. In the present work we compared the usefulness of immunoblotting (IB) and indirect immunofluorescence (IIF) in the diagnosis of pemphigus using monkey oesophagus (MO) and rabbit lip (RL) as epithelial substrates. Among 54 sera from patients with well-documented pemphigus (40 pemphigus vulgaris, PV, and 14 pemphigus foliaceus, PF), 46 (85%) proved positive by IFF (46 on MO and 41 on RL) as compared with 44 (81.5%) positive by IB. IIF and IB were equally sensitive (90%) for the diagnosis of PV whereas IIF (on RL) was more sensitive (71%) than IB (57%) for the detection of PF autoantibodies. However, when the two techniques were considered in combination, the sensitivity of the detection of pemphigus autoantibodies rose to 94.5%. An IB study would therefore be warranted in the presence of an (alleged) pemphigus serum that was IIF-negative since approximately 10% of these were found to be positive. Furthermore, the pattern of IB reactivity may assist in classification, since the 130- and the 160-kDa antigens seem specifically correlated with PV and PF, respectively.