ACCURACY OF INDIRECT IMMUNOFLUORESCENCE TESTING IN THE DIAGNOSIS OF PARANEOPLASTIC PEMPHIGUS

Background: Paraneoplastic pemphigus (PNP) is an autoimmune disease defined in part by autoantibodies with unique specificity. Initial reports suggested that indirect immunofluorescence with rodent bladder epithelium was highly reliable in detecting these autoantibodies. Objective: We compared the sensitivity and the specificity of indirect immunofluorescence in the diagnosis of PNP in a large number of cases. Methods: Indirect immunofluorescence was performed on stratified squamous epithelium of monkey esophagus and mouse tongue, bladder, liver, and myocardium. Sera were obtained from 28 patients with PNP and from 29 control subjects with autoimmune blistering diseases. Results: The sensitivity of murine bladder as a substrate was 75%, with a specificity of 83%. Indirect immunofluorescence on liver was specific (96.5%) but insensitive (43%). Sensitivity and specificity with myocardium were intermediate. Conclusion: Indirect immunofluorescence on murine bladder epithelium is an adequate screening test for PNP but is negative or indeterminate in as many as one fourth of patients. Negative indirect immunofluorescence does not exclude the diagnosis of PNP, and immunochemical techniques such as immunoprecipitation must be performed.