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Serologic tests for antibodies toBlastomyces dermatitidisare not thought to be useful for the diagnosis of blastomycosis, in part due to the low sensitivity of immunodiffusion and complement fixation. Earlier studies have shown that the enzyme immunoassay improves the sensitivity of antibody detection for the diagnosis of blastomycosis. Microplates coated with theB. dermatitidissurface protein BAD-1 were used for testing sera from patients with proven blastomycosis or histoplasmosis and controls. Semiquantification was accomplished by using standards containing human anti-B. dermatitidisantibodies. The antibodies were detected in 87.8% of the patients with blastomycosis by the enzyme immunoassay compared to 15.0% by immunodiffusion. The specificities were 99.2% for patients with nonfungal infections and healthy subjects and 94.0% for patients with histoplasmosis. The results were highly reproducible on repeat testing. When combined with antigen testing, antibody testing improved the sensitivity from 87.8% to 97.6%. Enzyme immunoassay detection of antibodies against BAD-1 is highly specific, has greatly improved sensitivity over immunodiffusion, and may identify cases with negative results by antigen testing. This assay has the potential to aid in the diagnosis of blastomycosis.

Having reported that pretreatment of serum samples with EDTA at 100°C improved the sensitivity for the detection of Histoplasma antigenemia, we have evaluated this method for the detection of Coccidioides antigenemia. Urine and serum samples from patients with coccidioidomycosis were tested using the MVista Coccidioides enzyme immunoassay, and serum samples with and without EDTA-heat treatment were tested. Antigenemia was detected in 28.6% of patients whose samples were not EDTA-heat treated and in 73.1% of those whose samples were treated. Antigenuria was detected in 50% of patients. Specificity of 100% was obtained in healthy subjects, but cross-reactions were seen in 22.2% of patients with histoplasmosis or blastomycosis. EDTA-heat treatment improves the sensitivity for the detection of Coccidioides antigenemia.

The second-generation Histoplasma antigen immunoassay is semiquantitative, expressing results as a comparison to a negative control, which requires repeat testing of the prior specimen with the current specimen to accurately determine a change in antigen. Reporting results in this manner often is confusing to the ordering physician and laboratory. Development of a quantitative assay could improve accuracy, reduce interassay variability, and eliminate the need to test the prior sample with the current sample in the same assay. Calibrators with known concentrations of Histoplasma antigen were used to quantitate antigen in specimens from patients with histoplasmosis and from controls. Samples from cases of disseminated histoplasmosis or other mycoses and controls were tested to evaluate the performance characteristics of the quantitative assay. Paired specimens were evaluated to determine if quantitation eliminated the need to test the current and prior specimens in the same assay to assess a change in antigen. The sensitivity in samples from patients with AIDS and disseminated histoplasmosis was 100% in urine and 92.3% in serum. Cross-reactions occurred in 70% of other endemic mycoses, but not in aspergillosis. Specificity was 99% in controls with community-acquired pneumonia, medical conditions in which histoplasmosis was excluded, or healthy subjects. A change in antigen level categorized as an increase, no change, or decrease based on antigen units determined in the same assay agreed closely with the category of change in nanograms/milliliter determined from testing current and prior specimens in different assays. Sensitivity, specificity, and interassay precision are excellent in the new third-generation quantitative Histoplasma antigen immunoassay.

Galactomannans (GalMs) are complex polysaccharides composed of D-galactose and D-mannose. Alkaline-extracted GalMs from Aspergillus fumigatus contain a core of (136)--D-mannopyranosyl residues, with (135)-linked -galactofuranosyl units. The pathogenic fungus Cryptococcus neoformans also contains complex capsular polysaccharides composed of glucuronoxylomannan (GXM) and galactoxylomannans (GalXM). GXM makes up about 90% of the capsular mass and is a polymer of up to six different repeating units that consist mostly of a linear (133)-mannan trisaccharide with side groups consisting of (132)-glucopyranosyluronic acid and (132)- and (134)xylopyranosyl (2, 6). Additionally, the mannan backbone of GXM is modified by acetyl groups. GalXM constitutes about 7% of the capsular mass (2) and has an (136) galactan backbone containing four potential short oligosaccharide branch structures. The branches are 3-O

Histoplasmosis is a common endemic mycosis in the Americas, often causing severe disease in patients with AIDS. Antigen detection has become an important method for rapid diagnosis of histoplasmosis in the United States but not in Central or South America. Isolates from patients in the United States are predominantly found to be class 2 isolates when typed using the nuclear gene YPS3, while isolates from Latin America are predominantly typed as class 5 or class 6. Whether infection with these Latin American genotypes produces positive results in the Histoplasma antigen assay has not been reported. In this study, we have compared the sensitivity of antigen detection for AIDS patients from Panama who had progressive disseminated histoplasmosis to that for those in the United States. Antigenuria was detected in the MVista Histoplasma antigen enzyme immunoassay (EIA) in 95.2% of Panamanian cases versus 100% of U.S. cases. Antigenemia was detected in 94.7% of the Panamanian cases versus 92% of the U.S. cases. Two clinical isolates from Panama were typed using YPS3 and were found to be restriction fragment length polymorphism class 6. We conclude that the MVista Histoplasma antigen EIA is a sensitive method for diagnosis of histoplasmosis in Panama. Progressive disseminated histoplasmosis (PDH) is a common and serious opportunistic disease among patients with AIDS in the United States and Latin America. In Panama, PDH occurred in 8% of hospitalized patients from 1997 to 2003 and was fatal in 12% of cases (6). The clinical picture was similar to that reported elsewhere and usually included fever, weight loss, and respiratory symptoms, often in association with diarrhea, as well as hepatosplenomegaly, hepatic enzyme elevation, and pancytopenia. Skin lesions were noted in 17% of the Panamanian cases (6), lower than the observed rate for cases from Brazil (66%) but higher than that for cases from the United States (3%) (7). Disease in patients in Mexico and Latin America has been described as being caused by isolates of Histoplasma capsulatum var. capsulatum that exhibit distinct genetic profiles in comparison to those from the United States (3, 8, 9). Keath et al. (9) first described typing based upon restriction fragment length polymorphism (RFLP) in the YPS3 gene. They showed that Panamanian strains were typed as YPS3 class 3, 5, or 6, while the North American strains were predominantly class 2. Later, Kasuga et al. used the DNA sequence substitution rates in four independent protein-coding genes to identify at least eight different genotypes, or clades (8). North American class 2 was the predominant genotype in the United States and Latin American group A in Latin America. Latin American group B was found only in Columbia and Argentina. Based on only four isolates from Panama included in the study by Kasuga et al., Panamanian strains included Latin American group A and a lone lineage, designated H81. The diagnosis of PDH relies on demonstration of the organism in clinical specimens or detection of antigen in body fluids (2). Histopathology may be falsely negative in up to 50% of patients, caused by sampling error, paucity of organisms, or inexperience of the pathologist. Culture may require several weeks to isolate and identify the organism and may be falsely negative for 15% of patients (13). Antigenuria can be detected in 95% of cases in patients with AIDS in the United States (4, 13) but has not been evaluated in Latin America. Whether genetic differences in Latin American isolates would affect the sensitivity for diagnosis by antigen detection is unknown. The prevalence of PDH in AIDS patients from Panama offered the opportunity to address this question.

We observed false-positive results in the Platelia Aspergillus enzyme-linked immunoassay (EIA) for specimens from patients with histoplasmosis and mice with experimental infection. Platelia Aspergillus EIA-positive specimens were negative in the second-generation Histoplasma antigen EIA. Care must be taken to exclude histoplasmosis for patients with positive Platelia Aspergillus EIA results.

Lindsley and colleagues ([5][1]) reported an antigen assay for diagnosis of histoplasmosis. Although they do not claim to have compared their test to that at MiraVista Diagnostics ([9][2]), the reader may draw that conclusion since the authors note that I provided antibodies, vaccine strain, and

The sensitivity of detection of antigenuria in patients positive by the MiraVista Diagnostics Histoplasma enzyme immunoassay (MVD EIA) was 44% with the IMMY ALPHA Histoplasma antigen EIA. The specificity was 84% with the IMMY EIA versus 98% with the MVD EIA. The correlation between assays for positive cases was weak ( r 2 = 0.430).