Fungal Biomarkers: Beta-D-Glucan and Aspergillus Galactomannan
Beta-D-Glucan:
• Polysaccharide cell wall component of many fungi
• Pathogens: Candida, Aspergillus
- Other positives: PJP, Histoplasma, Fusarium, Acremonium, Scedosporium, dermatophytes, Coccidioides
- Negative: Cryptococcus, Mucorales, Blastomyces dermatidis
• Sensitivity & Specificity:
- Serum BDG: Sens ~55-96%; Spec ~77-96%
- Higher specificity for invasive fungal infection (IFI) in hematologic malignancy (HM) pts --> cut-offs defined in clinical context of breakthrough IFI in HM
• False positives:
- IVIg, albumin, or other blood products
- IV penicillin formulations (e.g. amox-clav, not available in US)
- Hemodialysis with cellulose membranes (most dialyzer membranes synthetic now and should not increase BDG!)
- Cellulose filters for IV administration
- Gauze packing of serosal surfaces
- Infections with other pathogens with cellular beta-glucans (e.g. PsA, Nocardia, mycobacteria)
Aspergillus Galactomannan:
• Major polysaccharide constituent of Aspergillus cell walls
• Pathogens: Aspergillus
- Other Positives: Fusarium, Penicillium, Histoplasma, Blastomyces, Paecilomyces, Cryptococcus
- Negative: Mucorales
• Sensitivity & Specificity
- Serum GM: Sens/Spec ~80% for IA
- Most useful in high risk pts with HM and allogeneic HSCT
- +BAL GM does not differentiate colonization vs invasive disease
- Sensitivity decreased with: concurrent admin of mold-active antifungals, non-neutropenic pts, SOT recipients, CGD pts
• False Positives:
- Pip/Tazo, Amox/Clav (may be + as long as 5d after stopping abxs, but newer formulations post-2010 almost never +GM)
- IVIg, blood products
- Use of plasmalyte for BAL solutions causing positive BAL GM
- +GM more likely in 1st 100d following HSCT; with GIT mucositis or GVHD (leaky gut, translocation)
- Contamination of food with Aspergillus, closely related fungi
- Frozen ice-pops (in setting of GVHD)
ID Chalk Talks by Dr. Sara Dong
#Fungal #Biomarkers #BetaDGlucan #Aspergillus #Galactomannan #diagnosis #comparison
