Clinical Information

The Histoplasma Galactomannan EIA is a qualitative urine assay used as an aid in the diagnosis of histoplasmosis. It detects galactomannan antigen from Histoplasma capsulatum and should be interpreted in conjunction with clinical findings and other diagnostic studies, such as culture, histopathology, serology, and imaging.

Histoplasma capsulatum is a dimorphic fungus endemic to the Ohio and Mississippi River valleys and parts of Central and South America. Infection occurs through inhalation of fungal spores, commonly associated with exposure to bird or bat droppings. Clinical manifestations range from asymptomatic or mild flu-like illness to severe disseminated disease, particularly in immunocompromised patients.

Antigen detection offers a rapid diagnostic approach compared with fungal culture, which may require prolonged incubation and has variable sensitivity. Urine antigen testing is especially useful in suspected disseminated disease and in patients with advanced immunosuppression.

A negative result does not exclude histoplasmosis, as antigen levels may be below the limit of detection depending on disease burden, stage, or site of infection. False-positive results may occur due to cross-reactivity with other fungal organisms, including Blastomyces and Paracoccidioides. Results from different Histoplasma antigen assays are not interchangeable.

This assay is not intended for screening asymptomatic individuals or for monitoring response to therapy. Test interpretation depends on the pretest probability of disease, and testing should be performed only when there is appropriate clinical suspicion.