Antigen and Antibody Detection
An antigen enzyme immunoassay (EIA) for B. dermatitidis galactomannan is commercially available for the diagnosis of blastomycosis in humans and animals (MiraVista Diagnostics, Indianapolis, IN, USA).
In a study of 89 people with blastomycosis proven by histopathology or culture, the quantitative detection of antigenuria had a sensitivity of 90% (Connolly et al. 2012). Sensitivity was higher in patients with pulmonary disease (with or without extrapulmonary dissemination) compared to isolated extrapulmonary disease. The specificity was 99% in controls without fungal infections, but cross-reactivity occurred in 96% of controls with histoplasmosis (Connolly et al. 2012). However, another study from Marshfield, Wisconsin, evaluated antigen tests in persons with blastomycosis over a course of 10 years and found the sensitivity of antigenuria to be 76% (Frost and Novicki 2015).The use of the antigen EIA has also been studied for the diagnosis of canine blastomycosis (Spector et al. 2008). In a study of 46 dogs with blastomycosis, the sensitivities of antigen detection in urine and blood were 93 and 87%, respectively; false-positive results occurred in 2% of controls (Spector et al. 2008). Antigen detection is commonly used by veterinarians for the diagnosis of blastomycosis: Wisconsin veterinarians reported relying on this test more than any other to diagnose the disease (Anderson et al. 2014).
There is not currently a role for serological testing for Blastomyces-specific antibodies due to poor sensitivity (Smith and Gauthier 2015). An investigational EIA for antibodies against Blastomyces adhesion-1 (BAD-1) was reported to have sensitivities and specificities of 88% and 95-99%, respectively (Richer et al. 2014). Confirmatory studies are warranted.
8.4.4