What antigen test is used for invasive aspergillosis and detects a component of the Aspergillus cell wall?

• A. Beta-D-glucan (BDG) assay
• B. Aspergillus antibody test
• C. PCR for Aspergillus DNA
• D. Galactomannan enzyme immunoassay

Answer: (D)

Antigen detection for invasive aspergillosis centers on a specific component of the Aspergillus cell wall. Galactomannan is that component, and the galactomannan enzyme immunoassay tests for its presence in serum or bronchoalveolar lavage fluid. This makes it a focused test for diagnosing invasive aspergillosis in high-risk patients, since it directly detects the organism’s product rather than the host’s response or unrelated fungal elements. By comparison, beta-D-glucan is a broader fungal marker and not specific to Aspergillus; an Aspergillus antibody test checks the immune response rather than the pathogen itself; PCR targets fungal DNA rather than an antigen. Therefore, the galactomannan enzyme immunoassay best fits the description.