Diagnosis of paracoccidioidomycosis by passive haemagglutination assay of antibody using a purified and specific antigen-gp43.

Sheep red blood cells, treated with glutaraldehyde and sensitized with a purified Paracoccidioides brasiliensis antigen of molecular mass 43 kDa (gp43), were used to detect antibodies to P. brasiliensis by passive haemagglutination (PHA). Sera from 50 patients with paracoccidioidomycosis had PHA titres of > 1/800, and had antibodies detectable by immunodiffusion while antibodies to gp43 were detectable by PHA in sera from patients with histoplasmosis, aspergillosis, candidiasis, Jorge Lobo's disease or healthy people, only at titres of <1/100. Considering a cut-off at I/200, the sensitivity and specificity of PHA for paracoccidioidomycosis was 100%. Thus, the PHA test could be an efficacious method for routine serological diagnosis of paracoccidioidomycosis, with results in 1 to 2 h.