Case Study

“Lambeau” is a dog from Wisconsin that presented with clinical signs of cough, lethargy and anorexia. A neighbor’s dog recently died from blastomycosis, and Lambeau was known to frequent the same area as that dog. The veterinarian sent a urine specimen to MiraVista Diagnostics for MVista® Blastomyces Ag Quantitative EIA (Test code 316), and the urine antigen test result was negative. The veterinarian was concerned about a false negative.

Question: What additional tests were run to rule out a false negative?

The MVista® Blastomyces Canine IgG Antibody EIA (test code 330) and the MVista® Histoplasma Canine IgG Antibody EIA (test code 327) tests were performed on serum from Lambeau. The Blastomyces antibody result was positive at 17 antibody units, whereas Histoplasma antibody was negative. The veterinarian decided to treat with itraconazole for suspected blastomycosis, and Lambeau improved clinically.

The sensitivity of the MVista® antigen tests is high (90-95%); however, false negatives do occur, especially in cases with early or mild infection.
Although detectable antibody may have been present in this case due to previous exposure to Blastomyces, the potential recent exposure and response to therapy is supportive of early/mild blastomycosis.
Antibody testing is a useful adjunct test, particularly in cases with false negative or equivocal antigen results. For the most thorough evaluation of a patient, combined antigen and antibody testing will provide the highest sensitivity.

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