Test Code UHBAG Histoplasma and Blastomyces Antigen, Enzyme Immunoassay, Urine
Specimen Required
Supplies: Sarstedt Aliquot tube, 5 mL (T914)
Container/Tube: Plastic vial
Specimen Volume: 3 mL
Collection Instructions:
1. Collect a random urine specimen, with no preservative.
2. Do not centrifuge to remove particulates.
Useful For
Diagnosing Histoplasma capsulatum or Blastomyces dermatitidis infection without differentiation between the organisms
Monitor antigen levels following initiation of antifungal treatment
Method Name
Enzyme Immunoassay (EIA)
Reporting Name
Histoplasma/Blastomyces Ag, EIA, USpecimen Type
UrineSpecimen Minimum Volume
2.5 mL
Specimen Stability Information
Specimen Type | Temperature | Time | Special Container |
---|---|---|---|
Urine | Refrigerated (preferred) | 14 days | |
Frozen | 28 days | ||
Ambient | 7 days |
Reject Due To
Gross hemolysis | Reject |
Turbid Colored |
Reject |
Clinical Information
Blastomyces dermatitidis and Histoplasma capsulatum are dimorphic fungal agents with increasingly overlapping endemicity throughout the Midwestern, South Central, and Southeastern United States, particularly in regions around the Ohio and Mississippi River valleys, the Great Lakes, and the Saint Lawrence River. These agents are also found in regions of Canada.
These 2 fungi maintain a yeast form in the host at body temperature but are maintained as molds in the environment, which release spores that are inhaled by individuals leading to infection. Through phylogenetic analysis, B dermatitidis has been separated into 2 distinct species: B dermatitidis and Blastomyces gilchristii, both able to cause blastomycosis. B dermatitidis infections are frequently associated with dissemination, particularly in older patients, smokers, and immunocompromised hosts, while B gilchristii has primarily been associated with pulmonary and constitutional symptoms. Additional species of Blastomyces have recently been discovered and characterized; however, the performance characteristics of this assay for these species are unknown.
Approximately half of patients infected with Blastomyces will develop symptoms that are frequently nonspecific, including fever, cough, night sweats, myalgia or arthralgia, weight loss, dyspnea, chest pain, and fatigue. Symptoms may appear anywhere from 3 weeks to 3 months following infection.
For Histoplasma infections, clinical manifestations are largely dependent on the fungal burden at the time of exposure and the patient's underlying immune status. While the vast majority (>90%) of exposed individuals will remain asymptomatic, individuals seeking medical attention can present with a diverse set of symptoms ranging from a self-limited pulmonary illness to severe, disseminated disease. Individuals at risk for severe infection include those with impaired cellular immunity or have undergone organ transplantation, are HIV positive, or have a hematologic malignancy.
Diagnosis of blastomycosis and histoplasmosis relies on a combination of assays, including culture and molecular testing performed on appropriate specimens, and serologic evaluation for both antibodies to, and antigen released from, the organism. Although culture remains the gold standard method and is highly specific, these organisms can take several days to weeks to grow, and sensitivity is diminished in cases of acute or localized disease. Similarly, molecular testing offers high specificity and a rapid turnaround time, however sensitivity is imperfect. Detection of an antibody response to Blastomyces or Histoplasma offers high specificity; however, results may be falsely negative in patients who are acutely ill or are immunosuppressed.
Reference Values
Histoplasma/Blastomyces Antigen Result:
Not Detected
Histoplasma/Blastomyces Antigen Value:
Not Detected: 0.0 ng/mL
Detected: <1.3 ng/mL
Detected: 1.3-20.0 ng/mL
Detected: >20.0 ng/mL
Reference values apply to all ages.
Interpretation
Not detected:
No antigen from Histoplasma or Blastomyces detected. False-negative results may occur depending on extent of disease or site of infection. Repeat testing on a new specimen if clinically indicated.
Detected:
Antigen from Histoplasma or Blastomyces (unable to differentiate) was detected, below the limit of quantification (<1.3 ng/mL). Result should be correlated with clinical presentation, exposure history, and other diagnostic procedures, including culture, serology, histopathology, and radiographic findings to aid in the differentiation between histoplasmosis or blastomycosis.
Detected:
Antigen from Histoplasma or Blastomyces (unable to differentiate) detected. Result should be correlated with clinical presentation, exposure history, and other diagnostic procedures, including culture, serology, histopathology, and radiographic findings, to aid in the differentiation between histoplasmosis and blastomycosis.
Detected:
Antigen from Histoplasma or Blastomyces (unable to differentiate) detected, above the limit of quantification (>20.0 ng/mL). Result should be correlated with clinical presentation, exposure history, and other diagnostic procedures, including culture, serology, histopathology, and radiographic findings, to aid in the differentiation between histoplasmosis or blastomycosis.
Cautions
Due to significant cross-reactivity between galactomannan antigens from Blastomyces and Histoplasma, this assay does not differentiate between these 2 dimorphic fungal agents. To differentiate, consider fungal culture, molecular testing, or serology testing.
Positive results should be correlated with other clinical and laboratory findings (eg, culture, serology).
Low-level positive antigen levels may persist following resolution of infection and completion of appropriate treatment regimen.
Sensitivity of this assay to detect antigen from species other than Blastomyces dermatitidis or Histoplasma capsulatum is unknown.
False-positive results may occur less frequently with other dimorphic agents (eg, Coccidioides).
Day(s) Performed
Monday through Sunday
Report Available
Same day/1 to 3 daysPerforming Laboratory
Mayo Clinic Laboratories in RochesterTest Classification
This test was developed and its performance characteristics determined by Mayo Clinic in a manner consistent with CLIA requirements. It has not been cleared or approved by the US Food and Drug Administration.CPT Code Information
87449
LOINC Code Information
Test ID | Test Order Name | Order LOINC Value |
---|---|---|
UHBAG | Histoplasma/Blastomyces Ag, EIA, U | 105123-4 |
Result ID | Test Result Name | Result LOINC Value |
---|---|---|
UHBAR | Histoplasma/Blastomyces Ag Result | 104871-9 |
DEXBH | Histoplasma/Blastomyces Ag Value | 104872-7 |