Serological diagnosis of paracoccidioidomycosis using a Paracoccidioides spp. comercial antigen and the counterimmunoelectrophoresis method

PURPOSE: In-house Paracoccidioides spp. antigens are commonly used in the serological diagnosis of paracoccidioidomycosis (PCM). The sensitivity and specificity of a commercial Paracoccidioides spp. antigen was assessed for PCM serological testing. METHOD: Counterimmunoelectrophoresis and double immunodiffusion were used to evaluate the Paracoccidioides ID Antigen® reagent in sera from PCM cases and patients with other diseases. RESULTS: All active PCM sera (n=24) were reactive using counterimmunoelectrophoresis (sensitivity = 100%), including 11 cases of infection by P. brasiliensis sensu stricto and one by P. americana. Fifteen (88%) out of 17 sera from patients on treatment or cured were reactive, including one case of P. lutzii infection. One to three bands of antigen-antibody precipitate were observed on the agarose gel, with a predominance of two to three bands in the test with untreated PCM sera or at the beginning of antifungal therapy. All sera from patients with histoplasmosis (n=7), aspergillosis (n=5), and other diseases (n=27) tested negative (specificity = 100%). The overall sensitivity and specificity using the commercial antigen and double diffusion test were 75% and 100%, respectively. CONCLUSION: The commercial antigen performed satisfactorily and may contribute to the dissemination of the use of serological tests for the PCM diagnosis.