High prevalence of Clonorchis sinensis infection with sex and age related patterns and comparative evaluation of four diagnostic techniques in Hengzhou, China

Abstract Background Guangxi is one of the regions where clonorchiasis is endemic, with Hengzhou City notably standing out as a high-burden area for Clonorchis sinensis ( C. sinensis ) infection. This study aims to evaluate the prevalence of C. sinensis infection and compare the performance of available diagnostic methods to guide more precise clinical practices. Method This cross-sectional study included 1,220 hospitalized patients who provided fecal and serum samples in April–May 2025. Evaluated diagnostic methods included the reference standard hydrochloric acid-ether centrifugal sedimentation (HCl-EC), KU-F40 automated feces analyzer, direct smear (DS), and enzyme-linked immunosorbent assay (ELISA). Qualitative results were compared via Cochran’s Q test, followed by pairwise Bonferroni-corrected McNemar tests. Diagnostic performance metrics were calculated from 2 × 2 contingency tables. Sex and age subgroup analyses used McNemar or exact McNemar tests. Concordance of positive results and infection intensity was analyzed with Pearson’s chi-square test. The relationship between ELISA OD values and EPG counts was assessed using Spearman’s rank correlation analysis, and OD values were compared among infection intensity groups using the Kruskal–Wallis test with Dunn’s post hoc test. Results Using HCl-EC (reference standard), 362 patients (29.7%) were C. sinensis -positive. Prevalence was higher in men (44.2%) than women (11.6%) (χ 2 = 153.98, df = 1, P < 0.001), with 99.2% of infections in patients ≥ 30 years. Positive rates of HCl-EC, DS, KU-F40, and ELISA were 29.7%, 13.3%, 25.3%, and 65.0%, respectively. Pairwise agreement was highest for HCl-EC vs. KU-F40 (80.3%, κ = 0.51) and lowest for DS vs. ELISA (47.1%, κ = 0.13). Using HCl-EC as the reference method, ELISA showed the highest sensitivity (90.9%), whereas DS demonstrated the highest specificity (93.7%); KU-F40 achieved a sensitivity of 59.4% and a specificity of 89.2%. Positive result agreement was higher in high-intensity infection groups than low-intensity infection groups ( P < 0.001). ELISA OD values showed a weak positive correlation with EPG counts (ρ = 0.144, P = 0.009). OD values differed between the mild and moderate infection groups ( P = 0.01), but not between the other infection-intensity groups. Conclusions Clonorchis sinensis infection showed distinct sex and age related patterns. Considering both diagnostic performance and clinical practicality, the KU-F40 automated feces analyzer, with accuracy comparable to the HCl-EC method and advantages in cost, speed, and automation, has strong potential as an alternative for clonorchiasis screening. Targeted screening should be prioritized for high-risk populations, particularly males and individuals aged ≥ 30 years.