Antigen Test Evaluated for Blastomycosis

A commercially available assay for detection of Blastomyces dermatitidis antigen has been modified to permit quantitation in subjects with newly diagnosed blastomycosis.

An sandwich enzyme immunoassay (EIA) is available that will detect the antigen of the pathogenic mycoses B. dermatitidis in patients' serum, urine, cerebral spinal fluid, and other sterile body fluids.

In a study carried out at the University of Arkansas for Medical Sciences (Little Rock, AR, USA), samples were assayed from patients with newly diagnosed blastomycosis. Specimens from 27 subjects were analyzed and urine specimens from 25 healthy subjects and 25 subjects with conditions other than histoplasmosis or blastomycosis were analyzed to provide negative controls. If no antigen was detectable, the urine specimen was concentrated 10-fold and reanalyzed. Serum specimens were tested before and after treatment with ethylenediaminetetraacetic acid (EDTA) to dissociate immune complexes. Treatment of specimens with EDTA has not been shown to cause false-positive results in another fungal assay.

The assay used was the Mvista Blastomyces dermatitidis Antigen EIA, (MiraVista Diagnostics, Indianapolis, IN, USA). Of 27 patients, 23 (85.1%) had detectable B. dermatitidis antigen detected in their urine samples with a median of a 1.49 ng/mL, with a range of 0.21 ng/mL - 16.90 ng/mL. In two of these 23, positive results were obtained only after concentration of the urine specimen. Nine of 11 (81.8%) subjects had detectable B. dermatitidis antigen in their serum, including three subjects with negative results before treatment of serum with EDTA and positive results after EDTA treatment. B. dermatitidis antigen was not detected in specimens from 50 control subjects, but was detected in 15 patients with histoplasmosis. The authors concluded that the B. dermatitidis antigen was detected in most of the patients with blastomycosis and that it can be a useful tool for timely diagnosis. The study was published in February 2011, in the journal Diagnostic Microbiology and Infectious Disease.

Blastomycosis is an infection caused by inhaling microscopic spores produced by the fungus B. dermatitidis. Blastomycosis may be limited to the lungs or also involve the skin and bones. In its most severe form, the infection can spread throughout the body and become systemic. The fungus that causes the disease is found in moist soil and wood in the southeastern US, the Mississippi River valley, southern Canada, and Central America.

Related Links:
University of Arkansas for Medical Sciences
MiraVista Diagnostics