This assay indirectly detects anti-Blastomyces IgG by recognizing the BAD-1 repeat surface protein. During validation testing, the sensitivity was found to be 94.29% and specificity 95.00% with an assay cutoff of 14.0 EU. It offers an improvement over the current method of detecting antibodies by FID, where sensitivity has been reported as only 32%. Complement fixation is even less sensitive than FID.
The Blastomyces Antibody IgG EIA is useful for diagnosing blastomycosis in patients with negative antigen results. Secondly, when both Histoplasma and Blastomyces antigen assays are positive, comparing Histoplasma and Blastomyces antibody concentrations may assist in establishing the correct diagnosis. Additionally, following changes in antibody concentration via repeat testing may determine whether the infection has resolved or if relapse has occurred.