Enzyme Immunoassay (EIA) Tests

Blastomycosis presents a diagnostic challenge to the physician and laboratorian. The manifestations of most early infections overlap substantially with those of other respiratory infections. In addition, diagnosis by histologic or culture studies, though ideal, may take time or show negative results. Therefore, specific laboratory testing is usually required to establish a diagnosis of blastomycosis. Serologic tests have served for several decades as aids in the diagnosis and management of blastomycosis. Complement fixation (CF) and immunodiffusion (ID) have been the most commonly used serologic methods. The CF assay lacks both sensitivity and specificity and its performance is complex and labor-intensive. The CF assay exhibits low specificity due to cross-reactive antibodies recognizing carbohydrate moieties common to several fungi. Although the ID assay is more sensitive and specific than the CF assay, it takes 48 hours to perform and requires highly skilled personnel to properly interpret results. The OMEGA Blastomyces Total Antibody EIA, however, is a sensitive, specific, and rapid test for the qualitative detection of IgM and IgG antibodies against antigens from B. dermatitidis.

Complement Fixation (CF) Tests

CF tests with the purified ‘A’ antigen of B. dermatitidis, may only be positive in approximately 40% of confirmed cases. Thus, a negative test has little value and in no way excludes the possibility of active blastomycosis. Titers of 1:8 or greater are presumptive evidence of active or recent infection. The antigen frequently gives titers with confirmed cases of histoplasmosis and coccidioidomycosis. High titers or rising titers are suggestive of blastomycosis and serologic tests for other fungi should be performed simultaneously. For more complete serologic testing, immunodiffusion tests for blastomycosis should be performed in parallel with the CF tests.

Immunodiffusion (ID) Tests

Serologic testing for blastomycosis should be requested when a patient shows signs of a respiratory infection that progresses gradually and/or when lesions are present on the skin, a frequent sign of dissemination. Blastomycosis has no pathognomonic symptoms or specific radiologic features. The ID test for blastomycosis where antibodies are detected against the “A” antigen is specific (positive in approximately 80% of culturally proven cases) and positive reactions can be the basis for immediate treatment of the patient. The amount of antibody (i.e. titer) correlates with disease activity. Negative tests, however, do not exclude diagnosis of blastomycosis. If precipitins are demonstrated in the blastomycosis ID test, the testing of serum specimens by CF is unnecessary.

Immunodiffusion Plates

Enzyme Immunoassay (EIA)

cforms contact form by delicious:days

Complement Fixation (CF)

cforms contact form by delicious:days

Immunodiffusion (ID)

cforms contact form by delicious:days