Variability in galactomannan release by different Aspergillus species Low level of circulating galactomannan antigen Ĭhronic granulomatous diseases (CGD) and Job's syndrome.Mold-active antifungal treatment/prophylaxis GM screening should not be performed in neonates and children at low risk for IA ( Warris et al., 2019b). GM testing can be used both as a screening tool in pediatric patients considered at high risk for developing IA as well as a diagnostic tool in pediatric patients suspected of having developed IA, e.g., those with clinical symptoms or imaging abnormalities. In pediatric patients, the GM assay in serum seems to have a sensitivity and specificity profile that is similar to that in adults ( Lehrnbecher et al., 2016). In patients with hematologic malignancy or who have undergone hematopoietic stem cell transplantation (HSCT), the GM assay was most useful but in solid organ transplant (SOT) recipients the sensitivity and specificity of assay were 22% and 84% respectively ( Denning et al., 1997b). GM performance varies significantly in different patient cohorts. Low positive predictive value (PPV) of 26–53% and high negative predictive value (NPV) of 95–98% suggest that GM is more useful as a “screening” test to exclude the diagnosis of aspergillosis rather than as a confirmatory or diagnostic test. Measurement of GM antigen is currently recommended by the international guidelines ( Patterson et al., 2016 Ullmann et al., 2018) and included in the EORTC/MSG diagnostic criteria ( De Pauw et al., 2008).īased on a meta-analysis ( Pfeiffer et al., 2006), the sensitivity and specificity of serum GM in adult patients with proven IA, using a cut off index value > 0.5 for the diagnosis of IA, are 71% and 89% respectively. The Platelia™ Aspergillus enzyme-linked immunosorbent assay (ELISA) (Bio-Rad, France) is a standardized and well-validated test for the measurement of circulating antigen in serum ( Chai et al., 2012 Zhang et al., 2019 Lehrnbecher et al., 2016 Arvanitis et al., 2015) and BAL ( Zou et al., 2012 Heng et al., 2014 Zhang et al., 2013) from diverse patient populations. Galactomannan (GM) is a major polysaccharide compound of the cell wall of Aspergillus and some other ascomycete molds. The variability in response using different immunological assays highlights the problems inherent with antigenemia tests using patient's sera despite the incorporation of purified GM in different assay formats.Īlireza Abdolrasouli, Darius Armstrong-James, in Reference Module in Biomedical Sciences, 2021 Galactomannan However, significantly fewer were immunoreactive in ELISA, showing that GM was not suitable for detection of all aspergilloma patients using this technique. In the case of the aspergilloma study that comprised a substantially larger cohort of patients, all sera were positive in the immunodiffusion assay. Antigenemia was detected in both groups of patients with GM as the detector antigen.
Immunoreactivity of GM was tested in ELISA and immunodiffusion assays using sera from aspergilloma patients ( Latgé et al., 1994) and in counterimmunoelectrophoresis using sera from IA patients ( Reiss and Harris, 1979). The immunodominant epitope in the GM molecule is galactofuran and numerous intracellular and extracellular antigens with molecular masses > 40 kDa comprise this epitope ( Latgé et al., 1994 Morelle et al., 2005) including a lipopeptidogalactomannan of more than 100 kDa. fumigatus ( Latgé, 1999) that, in vitro, can be released as pure polysaccharide of approximately 20 kDa ( Latgé et al., 1994). Galactomannan is the only polysaccharide antigen characterized in A.
Galactomannan is an immunodominant polysaccharide component of the cell walls of Aspergillus and Penicillium species ( Beauvais et al., 2007 Fontaine et al., 2000 Latgé et al., 1994) and was the first antigen to be identified in animal models and in patients with IA. Thornton, in Advances in Applied Microbiology, 2010 D Galactomannan
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