Role of (1-->3)-beta-D-glucan in the diagnosis of invasive aspergillosis.

Measurement of serum (1-->3)-beta-D-Glucan (BG) is an aid in the diagnosis of fungemia and deep-seated mycoses, including invasive aspergillosis (IA). BG is present in the cell wall of most pathogenic fungi (including Pneumocystis jiroveci) in significant amounts with some notable exceptions such as Cryptococcus neoformans and Zygomycetes. Commercially available assays can detect serum BG concentrations as low as 1 pg/mL. Published validation studies have included patients with IA and other invasive fungal diseases (IFD). BG detection appears to be more sensitive than galactomannan detection in patients with IA, but BG's intrinsic lack of mycological specificity requires the integration of clinical, radiological, and microbiological data for proper interpretation. BG assay test characteristics can be used, for example, to exclude IA in some clinical scenarios, to increase the certainty of IA in the presence of an isolated positive galactomannan result or when testing follows initiation of antifungal treatment. BG may be falsely elevated in the serum in the absence of IFD in patients undergoing hemodialysis with cellulose membranes, in patients treated with immunoglobulin, albumin, or other blood products filtered through cellulose filters containing BG, and in patients with serosal exposure to glucan-containing gauze or to certain intravenous antimicrobials. These potential sources of false positivity should be considered when interpreting BG results. BG may be useful as a sensitive screening tool for surveillance of IA and other IFD in populations at risk. Stratified IFD screening and diagnostic strategies using both galactomannan and BG should be explored. Factors affecting the production and clearance of BG during IA and other IFD need additional study to further refine its diagnostic utility.