Evaluation of an enzyme immunoassay technique on detecting urinary Histoplasma capsulatum antigen in the diagnosis of disseminated histoplasmosis in Argentina.

INTRODUCTION

Histoplasmosis is a systemic mycosis of universal distribution, highly endemic in the Americas. It is caused by a dimorphic fungus Histoplasma capsulatum var. capsulatum. It affects both immunocompetent and immunocompromised individuals where progressive and disseminated forms are observed. A very important risk factor is HIV infection/AIDS, with a mortality rate of 20-40% in Latin America. The diagnosis of this mycosis is made by conventional and molecular methods or by antigen and antibody detection.

METHODS

In this retrospective, longitudinal and analytical study, carried out over a period of 2 years, the sensitivity (S) and specificity (E) of a commercial kit for the detection of Histoplasma antigen by EIA technique (HC-Ag) was evaluated in 50 patients with AIDSassociated histoplasmosis. In addition, its performance was compared with that of other diagnostic techniques routinely used in our laboratory.

RESULTS

HC-Ag had a S of 94%, E 96%, positive likelihood coefficient (CVP): 20.68 and negative likelihood coefficient (CVN): 0.06. The delay time of the results was 4 days, similar to that of antibody detection and n-PCR and much less than that of blood cultures. The combination of methods improved S to 100%; with similar values in E.

CONCLUSION

The HC-Ag method demonstrated its usefulness in the diagnosis of progressive disseminated histoplasmosis and the combination of methods is a good option to increase sensitivity and decrease the time to reach the diagnosis of certainty. This allows improving the strategy in the management of the disease and decreasing its case-fatality rate.