Elevated serum βglucan levels in cavitary pulmonary nocardiosis

Nocardiosis and elevated beta-d-glucan in solid organ transplant recipients

Beta-D-glucan (BDG) testing can expedite the diagnosis of invasive fungal infections in immunocompromised hosts. Elevated BDG levels have been reported in both in-vitro studies assessing cross-reactivity with Nocardia spp. and published cases of patients with nocardiosis, but there is little data on this association in solid organ transplantation (SOT) recipients. To explore this association, we conducted a case series of SOT recipients with culture-proven nocardiosis and BDG testing who received their care at our institution between 2016 and 2021. We found thirteen cases of nocardiosis in SOT recipients, of which three cases met our case definition of an elevated BDG. Their clinical courses are detailed in the present report. We found that BDG may be elevated in SOT with nocardiosis with no identified cause of false positive BDG, though a causal association cannot be determined. Future prospective studies that better evaluate the association between nocardiosis and BDG are warranted, as are studies that better characterize the possible variability in reactivity amongst Nocardia spp.

Specificity Influences in (1→3)-β-d-Glucan-Supported Diagnosis of Invasive Fungal Disease

(1→3)-β-glucan (BDG) testing as an adjunct in the diagnosis of invasive fungal disease (IFD) has been in use for nearly three decades. While BDG has a very high negative predictive value in this setting, diagnostic false positives may occur, limiting specificity and positive predictive value. Although results may be diagnostically false positive, they are analytically correct, due to the presence of BDG in the circulation. This review surveys the non-IFD causes of elevated circulating BDG. These are in the main, iatrogenic patient contamination through the use of BDG-containing medical devices and parenterally-delivered materials as well as translocation of intestinal luminal BDG due to mucosal barrier injury. Additionally, infection with Nocardia sp. may also contribute to elevated circulating BDG. Knowledge of the factors which may contribute to such non-IFD-related test results can improve the planning and interpretation of BDG assays and permit investigational strategies, such as serial sampling and BDG clearance evaluation, to assess the likelihood of contamination and improve patient care.