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Background Detection of antigen in BAL is useful for diagnosis of histoplasmosis. The MVista Histoplasma antigen enzyme immunoassay has been modified to permit quantification. The purpose of this study is to compare the sensitivity of the quantitative antigen detection assay with cytopathology and culture of BAL specimens. Methods BAL from patients with histoplasmosis who were evaluated at the Indiana University Medical Center and controls without histoplasmosis were studied. BAL fluid was tested in the quantitative Histoplasma antigen assay. Results Antigen was detected in the BAL in 93.5% of patients with histoplasmosis, 80% with blastomycosis, and 0% of controls with nonfungal infections. Antigen was detected in the urine of 79% and serum in 65% of patients with histoplasmosis. Cytopathology was positive in 48% and culture in 48% of patients with histoplasmosis, and 40% and 60% of patients with blastomycosis, respectively. Serology was positive in 65%. Combining BAL antigen detection and BAL cytopathology, both methods for rapid diagnosis, the sensitivity was 96.8% in histoplasmosis and 80% in blastomycosis. Conclusions Detection of antigen in BAL complements antigen detection in serum and urine as an objective diagnostic test for histoplasmosis.

Invasive fungal infections are often difficult to diagnose using radiology, culture methods, histopathology, or serology, and turnaround time is often lengthy. Antigen testing has been developed for several important invasive mycoses, offering rapid turnaround time and sensitivity comparable or superior to those of other methods. This review provides an update on rapid antigen testing for several invasive fungal infections, including histoplasmosis, blastomycosis, coccidioidomycosis, and aspergillosis and is intended as an addendum to previous reviews on the subject.

We evaluated the Fungitell beta-glucan (BG) test with specimens from patients with presumed histoplasmosis. The sensitivity of the test was 87% in histoplasmosis cases and had a specificity of 68% with controls. Histoplasmosis should be considered as a possible cause for a positive BG test, but such results may be found with many other conditions that are clinically similar to this fungal disease. Therefore, there is a need to conduct confirmatory tests for histoplasmosis in the appropriate clinical setting.