Expedient, effective analysis

Targeting pervasive infectious agents

Histoplasma capsulatum and Blastomyces dermatitidis are among the most prevalent fungal pathogens in the United States. Present in moist or fecund soils, these organisms release spores that can cause respiratory infection when inhaled. Among individuals infected with Histoplasma or Blastomyces, about half will develop symptoms. These can include fever, cough, chest pain, fatigue, headache, and body ache, but can progress to more severe illness and even death, particularly in patients who are immunocompromised.

While Histoplasma or Blastomyces have historically inhabited the Mississippi and Ohio river valleys, climate change has enabled an expansion of these organisms into a broader geographic range, putting more individuals at risk for infection.

A detection dilemma

Direct detection methods, such as culture and molecular testing, remain the gold standard for diagnostic confirmation of infection with Histoplasma and Blastomyces species. However, these methods often require invasive specimen collection that may not be suitable for all patients, and sensitivity can vary. Additionally, these organisms can take weeks to grow in culture, limiting their utility in acute diagnosis.

Detection of released antigens from these organisms is an effective alternative direct detection approach, which can quickly identify the presence of Histoplasma or Blastomyces infection. However, because of similar symptom presentation it’s nearly impossible to clinically distinguish which pathogen is causative, requiring physicians to often order two separate antigen tests. Additionally, the antigens released from Histoplasma and Blastomyces are very similar, leading to cross-reactivity between the individual assays. This frequently leads to Histoplasma antigens triggering positive results on Blastomyces testing and vice versa.

By the numbers


overall agreement in results from serum specimens tested using both Mayo Clinic Laboratories combined Histoplasma/Blastomyces antigen assay and individual Histoplasma and Blastomyces antigen assays.

Source: Internal Mayo Clinic data

Evidence-backed testing

Due to the antigen similarity between the organisms and to reduce the time and cost associated with processing two individual tests, Mayo Clinic Laboratories has developed an innovative serologic assay that detects antigens from both species in a single assay. Our combination evaluation capitalizes on the antigen similarity, identifying either fungal infection and facilitating early initiation of antifungal therapy.

Key testing

HIBAG | Histoplasma/Blastomyces Antigen, Enzyme Immunoassay, Serum

  • Detects for antigens from both Histoplasma and Blastomyces species.
  • Positively identifies infection and facilitates treatment initiation.
  • Saves time and money through combined testing approach.

Note: This evaluation does not differentiate between Histoplasma and Blastomyces species. For species-specific identification, culture, molecular testing, and serologic assessment are recommended.

Additional testing

An efficient, cost-effective, fungal testing alternative

Elitza Theel, Ph.D., explains how Mayo Clinic Laboratories' unique Histoplasma/Blastomyces test provides cost-effective evaluation for fungal infections that cause pulmonary illness. The assay reliably detects both Histoplasma and Blastomyces pathogens in a single test.

Learn how to order these evaluations at your institution.