Evaluation of two new enzyme immunoassay reagents for diagnosis of histoplasmosis in a cohort of clinically characterized patients.

The performance characteristics of the recently available analyte-specific reagent based enzyme immunoassay (ASR-EIA) and in vitro diagnostic (IVD) kit for urine Histoplasma antigen detection were evaluated in a cohort of 50 clinically characterized patients with histoplasmosis and 50 control patients. Overall sensitivity and specificity of the ASR-EIA were significantly improved compared with those of the IVD kit (sensitivity 72% vs. 22%, P<.001, specificity 98% vs. 84%, P = .014). Fourteen specimens from patients with clinically characterized histoplasmosis (five with pulmonary histoplasmosis and nine with progressive disseminated histoplasmosis) were falsely negative by ASR-EIA. All 10 specimens from patients with severe symptoms of progressive disseminated histoplasmosis were positive by ASR-EIA, although the average reading value of these 10 specimens was not significantly different from that of others with positive results. Compared to the MiraVista antigen assay, both the IVD kit and the ASR-EIA were significantly less sensitive in detecting Histoplasma antigen in the urine of patients with histoplasmosis. The ASR-EIA and MiraVista assay had comparable specificity. In conclusion, the ASR-EIA has improved performance compared with the IVD kit in the detection of Histoplasma antigen in the urine. However, users should be aware of the potential for false negative results using the currently recommended cutoff value.