Joe Wheat | John Witt | Heather Largura | Deborah Blue | Andrew Hanzlicek
Blastomycosis is endemic in the United States around the Great Lakes, St. Lawrence seaway, southeastern states, and less frequently elsewhere. Clinical findings include pulmonary disease alone or accompanied by disseminated disease. Antigen detection is a rapid method for diagnosis with recognition that cross reactions occur in histoplasmosis. From MiraVista’s review of data, urine antigen is positive in 4.2% and serum antigen 3.2% of large customers from Wisconsin, Minnesota, Arkansas, Tennessee, and Iowa, which are endemic for blastomycosis. Reviews by Drs. Smith and Kauffman on blastomycosis are recommended resources [1, 2].
The MiraVista Blastomyces antigen enzyme immunoassay (EIA) was introduced in 2003  and modified for quantification in 2011 , table 1. The sensitivity for detection of antigen in urine is 90% and 57% in serum , table 1. Specificity is 99% in controls with non-fungal diseases and healthy subjects and cross reactions occurred in 96% of patients with histoplasmosis. Day-to-day reproducibility (figures 1 and 2) and precision are excellent (table 2).
The EIA also is used for detection of antigen in bronchoalveolar lavage (BAL). The galactomannan antigen detected in histoplasmosis and blastomycosis is identical and cross reactions in the Histoplasma antigen EIA occurred in 80% (8/10) of BAL specimens from patients with blastomycosis . Blastomyces antigen also may be detected in CSF in patients with Blastomyces meningitis, table 3 .
Serial testing is used as an aid in judging success of treatment. Results of testing on different days exhibit reliable reproducibility, figure 1. Change in antigen concentration between current and prior specimens also show strong agreement, (R2 0.9338, slopes 0.8454, Y intercept 0.0401), figure 2. Testing at 3 months intervals during and at least one year after stopping treatment is recommended.
Gotham Blastomyces Antigen EIA
The Gotham EIA was introduced in 2021 . Results from testing are compared to those in the Gotham EIA. Positive agreement was 97.4% and negative agreement was 100%, but agreement of antigen concentration was low (y= 0.6067x + 2.4889, R2 0.2031). Urine from 4 patients with blastomycosis were positive in the MiraVista and Gotham EIA. Urine was tested from 9 patients with histoplasmosis, and antigen was detected in 5 (55.5%) in the Gotham EIA and 7 (77.7%) in the MiraVista EIA.
Advantages of MiraVista EIA
MiraVista has been offering its Blastomyces EIA for over 17 years. It has been validated for testing serum, urine, and BAL and is also offered for testing CSF as a rare specimen type pending validation, Table 4. These improvements have increased the sensitivity for diagnosis of different forms of blastomycosis.
Turn-around time is 1 day in 92%, 2 days in 98% and 3 days in 99%, providing rapid results permitting accurate diagnosis earlier, table 5.
Recommendations for Diagnosis
Table 1. Sensitivity and specificity
|Serum||Not done||Not done|||
1 Excludes cross-reactive galactomannan (histoplasmosis, paracoccidioidomycosis, talaromycosis)
Table 2. Precision MiraVista Blastomyces antigen EIA
|Calibrator||Mean (ng/mL)||Standard deviation (ng/mL)||Coefficient variation percent|
Table 3. Detection of antigen in the CSF from patients with Blastomyces meningitis
|Immunity||CSF Culture||Antigen n/mL||References|
Table 4. Antigen results from a single institution January 2020-June 2021
Table 5. MiraVista Blastomyces Antigen EIA
|Years’ personnel experience||108|
|Number of EIAs weekly||8|
|TAT||1-day 92%, 2-day 98%, 3-days, 99%|
Table 6. Importance of testing urine and serum: Results single institution
|Positive||Positive||37 (61.7%)||Highest sensitivity testing serum and urine|
|Positive||Negative||10 (16.7%)||Urine sensitive single test|
|Negative||Positive||6 (10%)||Urine alone misses 10%|
|Serum >urine||4 (6.7%)||Serum better for serial testing 6.7%|
Urine BLQ (< 0.2 ng/mL)
|3 (5%)||Positive serum true positive BLQ|
Figure 1. Reproducibility of Blastomyces antigen EIA for diagnosis
Figure 2. Reproducibility of Blastomyces antigen EIA for monitoring antigen clearance during treatment