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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.

SummaryAntigen detection is a useful adjunct for the diagnosis of histoplasmosis. The purpose of this study was to evaluate antigen detection in bronchoalveolar lavage (BAL) fluid using an improved second-generation Histoplasma antigen assay. Antigen was detected in 16 of 19 (84%) cases of histoplasmosis and 5 of 6 (83.3%) blastomycosis cases using the second-generation assay vs. 13 of 19 (68%) and 4 of 6 (66.7%), respectively, in the original assay. Ten-fold concentration permitted detection of antigen in an additional case of histoplasmosis and another with blastomycosis, for an overall sensitivity of 23 of 25 (92.0%). Specificity was 98.2% in both assays in controls with other pulmonary infections. These findings support the diagnostic utility of the second-generation assay in patients with pulmonary histoplasmosis and blastomycosis.

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.

Patients with histoplasmosis may test falsely negative for Histoplasma capsulatum antigenuria. In some cases antigen is present at levels below the assay's detection limit, and ultrafiltration could improve sensitivity. Antigen was detected following ultrafiltration in 73.8% of falsely negative specimens versus 2% of controls. Ultrafiltration improved sensitivity with a small reduction in specificity.

The sensitivity of detection of antigenuria in patients positive by the MiraVista Diagnostics Histoplasma enzyme immunoassay (MVD EIA) was 44% with the IMMY ALPHA Histoplasma antigen EIA. The specificity was 84% with the IMMY EIA versus 98% with the MVD EIA. The correlation between assays for positive cases was weak ( r 2 = 0.430).