Clin Microbiol Infect. 2021 Feb 15:S1198-743X(21)00080-X. doi: 10.1016/j.cmi.2021.02.005. Online ahead of print.
BACKGROUND: Diagnosing invasive or chronic fungal infections is a challenge, particularly in the immunocompromised host. Microscopy and culture remain the "gold standard" but are insensitive. The use of non-culture based techniques is recommended in conjunction with conventional methods to improve the diagnostic yield.
OBJECTIVES: The aim was to provide an updated 2021 inventory of fungal antigen and serology tests for diagnosing invasive and chronic fungal infections, the key focus was set on Aspergillus, Candida and Cryptococcus species.
SOURCES: Pubmed search for publications with the key words fungal antigen tests, laboratory-based diagnosis of invasive pulmonary aspergillosis (IPA), chronic pulmonary aspergillosis (CPA), invasive candidiasis (IC), invasive fungal infections, and cryptococcal infections published from 2017 to 2020.
CONTENT: Antigen assays such as the galactomannan (GM) and ß-D- glucan (BDG) detection systems are frequently used, yet these tests vary in sensitivity and specificity, depending on the patient population involved, specimens inspected, cut-offs defined, test strategy applied and inclusion or exclusion of possible fungal case definitions. Multiple different detection systems are available, with recently introduced new point-of-care (POC) tests such as the lateral flow device and the lateral flow assay. Despite a wide heterogeneity in populations evaluated, studies indicate a better diagnostic performance of broncho-alveolar lavage (BAL) GM in comparison to serum GM, and a suboptimal specificity of GM BALs (cut-off > 1) and serum BDG in non-neutropenic patients. POC-cryptococcal antigen tests show excellent performance.
IMPLICATIONS: There are fungal antigen detection tests available with excellent to reasonable clinical performance to diagnose invasive fungal infections. Only few assays are useful to monitor therapeutic response. There are multiple marketed IgG antibody tests to detect A. fumigatus antibodies, the titres vary widely and the performance differs significantly. In general, diagnostic tests are vulnerable to be affected by the host, the microbe and laboratory setting.