Combined detection of mannanaemia and anti-mannan antibodies as a strategy for the diagnosis of systemic infection caused by pathogenic Candida species

This study evaluated a combined serological strategy for diagnosing systemic candidiasis by detecting both mannanaemia (circulating mannan antigen) and anti-mannan antibodies using enzyme immunoassays (Platelia Candida Ag and Ab). Sera from 63 patients with proven candidosis caused by different Candida species were analyzed retrospectively. For C. albicans infections, the combined tests achieved 100% sensitivity, with 62% of patients showing positive antigenaemia and 67% showing antibody responses. For C. glabrata and C. tropicalis, sensitivities were 83% and 80% respectively. However, for C. parapsilosis, C. krusei, and C. kefyr, sensitivities were only 40-50%, likely due to limited epitope expression on these species' mannans. Serial sampling showed that at least one test became positive before positive blood cultures in 60% of patients with available pre-culture sera. Both tests reached maximum positivity around the time of positive mycological culture. The authors propose that regular serological monitoring of both markers in high-risk patients could enable earlier diagnosis of candidosis, particularly for the more pathogenic species.

Key findings

• Combined mannanaemia and anti-mannan antibody detection achieved 100% sensitivity for C. albicans infections and 91% overall sensitivity for C. albicans, C. glabrata, and C. tropicalis combined
• The serological tests detected infection before positive blood cultures in 60% of patients with available pre-culture samples, supporting early diagnostic potential
• Test sensitivity varies significantly by Candida species, with poor performance (40-50%) for C. parapsilosis, C. krusei, and C. kefyr due to reduced epitope expression on their mannans
• Converting the mannan detection assay from latex agglutination to enzyme immunoassay (EIA) format increased sensitivity 10-fold compared to previous methods