Screening for Schistosomiasis in a Non-Endemic Setting:  Accuracy of a Rapid Antibody Test Using Finger Prick Blood

Abstract

Background: Human schistosomiasis is a chronic neglected tropical disease caused by blood flukes of the genus Schistosoma, infecting 250 million people worldwide, mostly in sub-Saharan Africa. Recently, thousands of cases have been reported in immigrants to non-endemic countries, including Italy. Serological screening is recommended but so far, no accurate point-of-care (POC) and lab-free test is available.

Methods: Prospective evaluation of the accuracy of a new POC immunochromatographic test (Black- ICT, IgG-IgM) for schistosomiasis screening, to be used on blood obtained by finger prick. The recruitment of eligible immigrants in Italy took place at the University Hospital of Bologna from September 2021 to May 2023. Subjects were consecutively recruited as part of a screening programme, regardless the presence of symptoms. The other tests used were microscopy on stools and urine and three antibody assays: a serum-ICT (SCHISTOSOMA ICT IgG-IgM, LDBIO Diagnostics), an ELISA (NovaLisa Schistosoma mansoni IgG, Novatec) and a Western Blot (SCHISTO II Western Blot IgG, LDBIO Diagnostics). Statistical analysis was performed using a Bayesian latent class model.

Findings: 198 subjects were enrolled in the study. Black-ICT had a sensitivity of 86.6% (95% credible interval 76.9-94.7) and a specificity of 88.4% (82.0-94.3). At the estimated prevalence level for the study sample, 32.6% (25.5-40.0), the positive and negative predictive values were 78.2% (66.4-89.4) and 93.2% (87.7-97.6), respectively. Good agreement was found with the other antibody tests, with the highest sensitivity being observed for serum-ICT (91.0%, 84.7-96.4) and the highest specificity for ELISA (92.6%, 87.5-96.7).

Interpretation: The novel POC test for schistosomiasis showed satisfactory results and could greatly improve the detection of this parasitic infection in non-endemic settings, as the simple, lab-free approach could greatly expand the target group.

Funding: Italian Ministry of Health.

Declaration of Interest: All authors declare no competing interests.

Ethical Approval: The study was approved by the Ethics Committee of the Area Vasta Emilia Centro (CE-AVEC), Protocol n. 4144/2020. All subjects signed an informed consent.

Keywords: Schistosomiasis, Immunochromatographic Test, finger-prick blood, screening