Serological Comparison of Native Antigen ELISAs with Rapid ICT Test Kits for the Diagnosis of Human Alveolar and Cystic Echinococcosis in China

Abstract

Background: The aim of this study was to compare the diagnostic performance of native antigen ELISAs and ADAMU-AE/CE commercial ICT test kits in subjects either exposed to Echinococcus infection or with clinically diagnosed alveolar (AE) or cystic (CE) echinococcosis. Methods: A total of 370 subjects with a previous clinical confirmation of CE or AE from northwestern China were recruited. Serum samples were also obtained from 3923 children/teenagers during a community survey. All sera were tested using native antigen ELISAs. The ADAMU-AE/CE test kits were subsequently used for the serology of the 370 clinically confirmed individuals and of 251 children/teenagers that were ELISA antibody-positive for both Echinococcus species but ultrasound-negative during baseline survey. An analysis of the association between the serological tests and ultrasound classification was carried out amongst 89 AE and 164 CE cases. A Kappa consistency analysis was undertaken to compare the diagnostic performance of the native antigen ELISAs and the ADAMU kits and the ultrasound imaging results. The χ² test was also used for a comparison of the different seropositivity rates between the groups. Findings: There was poor consistency (Kappa = 0.26 and 0.28 for AE and CE respectively) between the native antigen ELISAs and the ADAMU kits for the diagnosis of AE and CE among the cases and the surveyed children/teenagers, but a relatively good consistency (Kappa = 0.63) between the ADAMU-AE kit and ultrasound observations for the AE cases. Additionally, of the 251 teenagers co-positive for both AE and CE antibodies by the native antigen ELISAs, only one was found positive by the ADAMU-AE kit, verified as a new AE case on subsequent ultrasound follow-up. The remainder (N = 250) were negative by serology using the ADAMU-AE/CE kits and by ultrasound examination. The two native antigen ELISAs did not discriminate well between cases of clinically diagnosed AE and CE. In contrast, ADAMU-AE and ADAMU-CE commercial ICT test kits readily differentiated cases of AE from CE with specificities of 99% for AE and 100% for CE. Conclusions: The ADAMU-AE/CE kits proved reliable, accurate, and amenable diagnostic tools in the clinical setting for confirmation of suspected AE/CE cases. The native antigen ELISAs tests can provide useful information on the level of human exposure to Echinococcus infection.

The Diagnostic Challenge of Cystic Echinococcosis in Humans: First Assessment of Underreporting Rates in Mongolia

“…Resources for serological tests at provincial level, scoring 1.83, were another challenge addressed by health professionals. Although currently available conventional serological methods, such as the ELISA test, are not yet fully reliable for diagnostic purposes, significant progress in their sensitivity and specificity has been made in recent years [18][19][20]. However, in Mongolia, where maintaining lab facilities and resources in remote areas is difficult, easily applicable tests such as Rapid Diagnostic Tests (RDTs) might be more practical at the provincial level.…”

“…While the sensitivity and specificity of various antigens have been established, current assays still face challenges in standardization and accuracy [18]. Debates persist regarding their clinical diagnostic and screening utility, with serodiagnostic performance influenced by factors like cyst location, stage, and size, while these variables remain inadequately assessed to date [19,20]. A recent review confirmed that cyst staging significantly influences the sensitivity of ELISA tests, with sensitivity ranging from 60-90% for CE1-CE3 stages, but dropping below 50% for CE4, CE5, and inactive cysts [8].…”