Detection of serum anti-candidalysin IgG by indirect ELISA: a novel auxiliary tool for diagnosing invasive candidiasis in a preliminary pediatric study.

Invasive candidiasis (IC) is the most common fungal infection in clinical settings, yet early diagnosis remains challenging. Candidalysin, a key virulence factor in invasive infections, exhibits site-specific pathogenicity. Our study identifies candidalysin as a serodominant antigenic peptide and reveals significantly elevated serum anti-candidalysin IgG levels in IC across diverse anatomical sites, suggesting its potential as a novel diagnostic biomarker. To evaluate this, we developed an indirect enzyme-linked immunosorbent assay (ELISA) to quantify serum anti-candidalysin IgG. The assay was validated in two distinct validation subsets using a 5-year cohort comprising 121 proven, probable, or possible IC cases from Hunan Children's Hospital, alongside 105 non-IC controls (patients with other infections and healthy individuals). In validation set 1, comparing proven IC cases (n = 20) to non-IC controls, the cutoff increased to 0.1768 ng/mL, with an area under the curve (AUC) of 0.818 (95% CI: 0.736-0.899), 80% sensitivity, and 73.3% specificity. In validation set 2, receiver operating characteristic (ROC) analysis comparing proven/probable IC cases (n = 77) to non-IC controls (n = 105) yielded an AUC of 0.870 (95% CI: 0.821-0.919) at an optimal cutoff of 0.1647 ng/mL, demonstrating 87% sensitivity and 70.5% specificity. These findings establish the indirect ELISA for anti-candidalysin IgG as a robust diagnostic tool for IC. Additionally, the assay effectively discriminates colonization from invasive infection at non-sterile sites in suspected cases, offering valuable guidance for antifungal therapy and prophylaxis.IMPORTANCEThe indirect enzyme-linked immunosorbent assay (ELISA) for detecting serum anti-candidalysin IgG exhibits robust diagnostic performance in invasive candidiasis, demonstrating particular utility in distinguishing commensal colonization from invasive infection in cases of suspected deep-seated candidiasis. This assay represents a valuable adjunctive tool for both clinical diagnosis and therapeutic management of invasive candidiasis.