Systematic Evaluation of Four Cysteine Proteases (CsCP1–4) from Clonorchis sinensis for Serodiagnosis: From Single-Antigen Screening to Multi-Antigen Modeling

BACKGROUND: CP1-4) for human clonorchiasis. METHODS: CP1-4. The assay was validated using 180 microscopy-confirmed positive and 148 negative control sera. Samples were randomly split into training and validation sets (7.5:2.5). Diagnostic performance of single antigens and their combinations was evaluated using univariate and multivariate logistic regression and compared with a commercial kit. Key metrics included the area under the curve (AUC), sensitivity, specificity, accuracy, F1-score, and Kappa coefficient. RESULTS: CP4-IgG4 (0.773) indicated substantial agreement with the microscopic standard. Multi-antigen combinations (triple or quadruple) further enhanced performance, achieving sensitivity and specificity > 98% with an AUC approaching 1.0. CONCLUSIONS: CP2-IgA pair suggests that detecting fecal secretory IgA could be a novel avenue for non-invasive, self-testing applications.