Background and design: Ninety-seven patients suffering from a pruritic dermatosis were screened for the detection of bullous pemphigoid (BP) antibodies (ab) using the Western immunoblot (WB) analysis technique.
Results: Twenty-four patients (25%) reacted at least twice with the BP antigen on WB analysis at a 1/10 dilution: seven had typical BP, four had papular BP, 10 had pruritus and prurigo of unknown origin, two had eczema, and one had lichen planus. This corresponds to 13% of BP-type ab in patients who did not fulfill criteria for BP. Therefore, we did the following: (1) tested a control group of 24 subjects; (2) assessed the reproducibility of the WB method by retesting the same serum samples on different epidermal extracts; and (3) estimated the BP ab titer. None of the 24 control subjects had detectable BP ab, and reproducible results were obtained in all groups when serum samples were retested at the 1/10 dilution. Although 86% (6/7) of patients with BP had BP ab titers of 1/100 or greater, only 60% (6/10) of the group with pruritus and prurigo and 33% (1/3) of the group with eczema reached such titers.
Conclusion: These results indicate that due to its sensitivity, the WB method can detect low titers of BP ab in patients with pruritic dermatoses who did not fulfill criteria for BP, and therefore we question the specificity of this method.