Comparison of the Enzyme Immunoassay, Immunodiffusion, and Complement Fixation Tests in Detecting Antibody in Human Serum to the A Antigen ofBlastomyces dermatitidis^1–3

Abstract

Using a new enzyme immunoassay (EIA) and standard immunodiffusion (ID) and complement fixation techniques for antibody to the A antigen of Blastomyces dermatitidis, we tested serum from 27 patients with blastomycosis diagnosed histopathologically or by culture; 20 with diagnoses made during 1981 through 1983 (Group A) and 7 during 1974 through 1976 (Group B). We also studied 30 control subjects with Mycoplasma pneumoniae infection (17 subjects), histoplasmosis (6 subjects), coccidioidomycosis (1 subject) and no known disease (6 subjects). Detectable antibody by all 3 tests was present more often for Group A than for Group B, possibly because of delay in testing. Enzyme immunoassay was the most sensitive test; a 1:8 or greater titer was present in acute-phase serum of all Group A patients tested, and a 1:64 or greater titer was associated with disseminated disease (p = 0.003). A positive ID was also more common in disseminated (88%) than in localized (33%) disease. Enzyme immunoassay titers of 1:16 were present in 4 control subjects, 3 with histoplasmosis. The 100% predictive values of a negative EIA and positive ID suggest that these tests are useful for serologic screening (EIA) and serologic confirmation (ID) of suspected blastomycosis, particularly in disseminated disease. Enzyme immunoassay titers of 1:32 or greater strongly support the diagnosis and titers of 1:16 or less may indicate localized disease or be nonspecific. None of the serologic tests predicted disease progression or reactivation.

Isolation, purification, and radiolabeling of a novel 120-kD surface protein on Blastomyces dermatitidis yeasts to detect antibody in infected patients.

“…10 histoplasmosis patients had acute pulmonary infection, 10 had chronic pulmonary disease, and 4 had disseminated disease; no clinical information was available in the remaining 10 histoplasmosis patients. 7 coccidioidomycosis patients had acute pulmonary infection, 5 had chronic pulmonary disease, and 10 had disseminated disease. 10 sporotrichosis patients had isolated cutaneous disease and 1 had cavitary pulmonary disease.…”

“…Both antigens are impure (5,6), they appear to be a mixture ofcell wall components, and tests employing them are not widely available. A further problem with serologic tests using A antigen has been diminished specificity as sensitivity is increased by enzyme immunoassay techniques (7)(8)(9). This problem results from A-antigen impurity and the extensive sharing of cell wall components between dimorphic fungi, particularly B. dermatitidis and Histoplasma capsulatum.…”

Development of a Highly Sensitive and Specific Blastomycosis Antibody Enzyme Immunoassay Using Blastomyces dermatitidis Surface Protein BAD-1

“…The diagnosis of blastomycosis is usually based upon direct visualization of broad-based budding yeast in a clinical specimen or culture of the organism (3)(4)(5)(6)(7). The methods can be time-consuming or require invasive procedures.…”

“…According to a recent review, an agar gel immunodiffusion (AGID) test showed a sensitivity of only 32%, and in previous studies less than half of blastomycosis cases were seropositive (6)(7)(8)(9)(10)(11). Complement fixation is less sensitive than AGID in patients with blastomycosis, is more difficult to perform, and offers no advantages over AGID (7)(8)(9).…”

“…The enzyme immunoassay (EIA) is more sensitive than the AGID test, but previous tests were falsely positive in one quarter of patients with histoplasmosis (7)(8)(9)(10)(11). In one study using a commercially available EIA, the sensitivity was 100%, but false positives in nonfungal controls were detected in 20% of cases (10).…”