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This case describes the diagnostic challenges associated with false-positive β-D-glucan results in critically ill patients, focusing on a patient with severe Pseudomonas pneumonia.

May 20, 2026

A49-29 False Positive β-d-glucan in Severe Pseudomonas Pneumonia Mimicking Invasive Fungal Infection: Balancing Clinical Judgment With Diagnostic Stewardship

Key Points

This case describes the diagnostic challenges associated with false-positive β-D-glucan results in critically ill patients, focusing on a patient with severe Pseudomonas pneumonia.
Case study of a 44-year-old woman with severe Pseudomonas pneumonia requiring VV ECMO
Assessment of β-D-glucan levels and microbiological cultures
Integration of clinical judgment with diagnostic data to guide treatment decisions.
Serum β-D-glucan was positive at 130 pg/mL despite negative blood cultures for fungal infections.
Subsequent cultures confirmed Pseudomonas aeruginosa as the causative pathogen, leading to a change in therapy.
The case emphasizes the need for cautious interpretation of β-D-glucan results in ICU settings to avoid unnecessary antifungal treatments.

Abstract

Abstract False-positive serum β-D-glucan (BDG) results are a recognized diagnostic challenge in the evaluation of invasive fungal infections, particularly in critically ill patients. The test’s limited specificity in intensive care unit (ICU) settings has been ascribed to various confounding factors, including certain antibiotics, hemodialysis filters, and severe bacterial infections.This case describes a 44-year-old woman with severe Pseudomonas aeruginosa pneumonia, diabetic ketoacidosis, and septic shock, who developed refractory hypoxemia requiring veno-venous extracorporeal membrane oxygenation (VV ECMO). Despite negative blood cultures and radiological workup, serum BDG was positive (130 pg/mL), prompting empiric antifungal therapy. However, no further objective evidence of fungal infection was identified despite a repeated positive BDG level. Subsequent sputum cultures grew Pseudomonas aeruginosa, leading to de-escalation from antifungal to targeted antipseudomonal therapy, with notable clinical improvement. This case highlights the diagnostic limitations of BDG in ICU populations, where false positives are frequently associated with severe Gram-negative infection and other confounders. However, as demonstrated in our case, associations with localized infections may also subscribe to BDG elevation in the absence of invasive fungal disease. Recognizing this potential relationship is essential to avoid unnecessary antifungal exposure, reduce drug-related toxicity, and prevent the emergence of antifungal resistance. Given these limitations, we suggest clinicians should interpret BDG results with caution and in conjunction with the overall clinical picture, microbiological data, and radiologic findings to avoid unnecessary antifungal exposure. This abstract is funded by: None

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