Blastomyces dermatitidis antigen detection by quantitative enzyme immunoassay.

Area of Science:

• Medical Mycology
• Diagnostic Immunology
• Infectious Diseases

Background:

• The non-quantitative MVista Blastomyces antigen assay limited assessment of antigen level changes.
• Sensitivity of the previous assay in serum was not fully evaluated.
• Accurate quantification is crucial for monitoring Blastomyces infection progression.

Purpose of the Study:

• To evaluate a quantitative Blastomyces antigen assay for urine and serum.
• To assess the utility of antigen quantification in monitoring treatment response.
• To improve the detection of Blastomyces antigenemia.

Main Methods:

• Utilized calibrators with known Blastomyces galactomannan concentrations to quantify antigen in patient samples.
• Tested paired urine specimens to determine if quantification negates the need for concurrent testing.
• Evaluated serum pretreatment with EDTA at 104°C to improve antigenemia detection.

Main Results:

• Detected antigenuria in 89.9% of blastomycosis patients with 99.0% specificity against non-fungal infections.
• Observed cross-reactivity in 95.6% of histoplasmosis patients, indicating limited specificity.
• Quantification allowed accurate assessment of antigen level changes without concurrent testing.
• Serum pretreatment increased antigenemia detection sensitivity from 35.7% to 57.1%.

Conclusions:

• The quantitative assay effectively detects Blastomyces antigen in urine and serum.
• Quantification simplifies monitoring of antigen levels, eliminating the need for concurrent specimen testing.
• Serum pretreatment significantly enhances the sensitivity of antigenemia detection.
• Antigen detection alone cannot differentiate between blastomycosis and histoplasmosis.