A known limitation of the beta-D-glucan assay in screening for fungal infections is that it may yield what?

• A. It is completely specific for invasive aspergillosis
• B. False positives and false negatives
• C. Requires tissue biopsy for results
• D. Not used in clinical practice

Answer: (B)

Beta-D-glucan serves as a broad screen for invasive fungal infections because it detects a shared component of many fungal cell walls. But this broad utility comes with imperfect accuracy. Positive results can occur in patients without invasive disease due to cross-reactivity or exposure to glucan-containing substances, leading to false positives. On the flip side, a negative result does not rule out infection, because some fungi (such as Mucorales and Cryptococcus in certain contexts) may not produce detectable levels of beta-1,3-D-glucan, the fungal burden may be too low early in infection, or antifungal therapy can reduce circulating glucan levels, causing false negatives. Thus, the assay is an adjunctive tool with limitations, rather than a definitive test.