There is an increasing incidence of fungal infections by both primary and opportunistic pathogens, especially in immunocompromised patients. Invasive fungal diseases, as opportunistic infections, are common among hematological malignancy and AIDS patients and account for a growing number of nosocomial infections, particularly among organ transplant recipients and other patients receiving immunosuppressive treatments. Common primary human fungal pathogens are Candida spp. and Aspergillus spp., opportunistic fungal pathogens, including Fusarium spp., Trichosporon spp., Saccharomyces cerevisiae, Acremonium, Coccidioides immitis, Histoplasma capsulatum, Sporothrix schenckii and Pneumocystis carinii. The (1→3)-ß-D-glucan produced by these organisms can be detected by the Fungitell assay.
Normal human serum contains low levels of (1→3)-ß-D-glucan, typically 10-40 pg/mL, presumably from commensal yeasts present in the alimentary canal and gastrointestinal tract. Most pathogenic fungi have (1→3)-ß-D-glucan in their cell walls and minute quantities are sloughed into the circulation during the life cycle. Thus, (1→3)-ß-D-glucan appears in the serum in cases of invasive fungal infection (IFI). Monitoring serum glucanemia for evidence of elevated and rising levels provides a convenient surrogate marker for IFI. Levels above 80 pg/mL, in at-risk patients, are considered positive. The Fungitell assay is indicated for presumptive diagnosis of fungal infection. It should be used in conjunction with other diagnostic procedures. The Fungitell assay does not detect certain fungal species such as the genusCryptococcus, which produces very low levels of (1→3)-ß-D-glucan. This assay also does not detect the Zygomycetes, such as Absidia, Mucor, and Rhizopus, which are not known to produce (1→3)-ß-D-glucan.