False-positive beta-glucan test due to beta-glucan component in sterile gauze during treatment of fungal sepsis: a case report.

Background: The (1,3)-β-D-glucan (BDG) assay, commonly referred to as the G test, is influenced by numerous factors and is prone to false-positive and false-negative results, particularly false positives, which pose significant challenges for clinical diagnosis and treatment of invasive fungal diseases (IFDs). Case presentation: We report a patient with a non-healing wound and enterocutaneous fistula following abdominal wall hernia surgery, who responded effectively to antifungal therapy for fungal sepsis. Despite persistently negative blood cultures, the (1,3)-β-D-glucan (G-test) remained positive for three consecutive months. Through systematic exclusion of confounding factors, including antibiotics, bacterial infections, blood products, fungal preparations, and specimen-related issues, the persistent elevation in G test results was ultimately attributed to contamination by medical sterile gauze. The patient eventually recovered from fungal sepsis and was discharged. Conclusion: When microbiological evidence for infection is insufficient and clinical symptoms improve with a clear therapeutic response, yet the G test remains persistently positive at high levels over an extended period, careful analysis of potential causes is essential. The G test result should not be blindly used as an indication for antifungal therapy. Medical sterile gauze, cotton swabs, and cotton balls contain high concentrations of BDG, which may lead to false-positive results and should be carefully considered during differential diagnosis.