Detection of Histoplasma capsulatum antigen in Panamanian patients with disseminated histoplasmosis and AIDS

Abstract

Histoplasmosis is a common endemic mycosis in the Americas, often causing severe disease in patients with AIDS. Antigen detection has become an important method for rapid diagnosis of histoplasmosis in the United States but not in Central or South America. Isolates from patients in the United States are predominantly found to be class 2 isolates when typed using the nuclear gene YPS3, while isolates from Latin America are predominantly typed as class 5 or class 6. Whether infection with these Latin American genotypes produces positive results in the Histoplasma antigen assay has not been reported. In this study, we have compared the sensitivity of antigen detection for AIDS patients from Panama who had progressive disseminated histoplasmosis to that for those in the United States. Antigenuria was detected in the MVista Histoplasma antigen enzyme immunoassay (EIA) in 95.2% of Panamanian cases versus 100% of U.S. cases. Antigenemia was detected in 94.7% of the Panamanian cases versus 92% of the U.S. cases. Two clinical isolates from Panama were typed using YPS3 and were found to be restriction fragment length polymorphism class 6. We conclude that the MVista Histoplasma antigen EIA is a sensitive method for diagnosis of histoplasmosis in Panama.

FIG. 1.

Urine and serum antigen in patients with AIDS and PDH. The solid horizontal line represents the cutoff for positivity and the dashed lines the lowest (0.6 ng/ml) or highest (39 ng/ml) calibrator. Each point represents a single case.