Application of indirect immunofluorescence on the diagnosis of pemphigus

Pemphigus is an autoimmune bullous disease, and although several diagnostic methods are now in use indirect immunofluorescence (IIF) is still considered an important tool for diagnosing pemphigus because of its convenience, repeatability, and reduced pain for patients. The goal of the present study was to evaluate the diagnostic value of IIF on normal human skin (NS), monkey esophagus (ME), and salt-split skin (SS) for better diagnosis of pemphigus. Clinical data of 70 patients with pemphigus and 56 control were collected. IIF on NS, ME, and SS were assessed separately by observing fluorescein deposition and comparing its differentiation to different kinds of pemphigus and its sensitivities and specificities to different substrates. Intercellular deposition of IgG was visible when IIF on NS, ME, and SS were positive in patients with pemphigus. Their corresponding sensitivities and specificities were 30.0%, 84.3%, and 70.0% and 96.4%, 96.4%, and 94.6%, respectively. The differences in sensitivity were statistically significant between NS and ME and between NS and SS (P<0.001) and the specificities among the three substrates were not statistically significantly different (P>0.05). As for different types of pemphigus, the sensitivities between NS and ME and between NS and SS were statistically significantly different in both Dsg1- and Dsg3-positive and only Dsg1-positive patients with pemphigus (P<0.01); the sensitivities between NS and ME were statistically significantly different only in Dsg3-positive patients with pemphigus (P<0.001); there were no statistically significant differences between ME and SS. We therefore propose that ME is a good substrate for pemphigus diagnosis with higher sensitivity and superior to NS, particularly for patients with anti-Dsg3 antibodies. SS is a good alternative substrate to ME with almost identical higher sensitivities and specificities for diagnosis of pemphigus.