Detection of Histoplasma capsulatum antigenuria by ultrafiltration of samples with false-negative results.

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.