Diagnostic Circulating Anodic Antigen Test for Schistosoma haematobium Infections

The upconverting phosphor lateral flow (UCP-LF) circulating anodic antigen (CAA) test is highly sensitive and specific for Schistosoma haematobium (S haematobium) in pregnant women and performs well for urogenital schistosomiasis, according to preliminary results of the freeBILy study published in BMC Infectious Diseases.

The control and prevention of schistosomiasis is based on praziquantel (PZQ) treatment. Egg microscopy is the current standard for schistosomiasis diagnosis but is not widely used due to its low sensitivity. Investigators conducted a prospective, observational study to evaluate the accuracy of CAA test to diagnose Schistosoma infections in pregnant women and validated CAA as an endpoint measure for PZQ efficacy (ClinicalTrials.gov identifier: NCT03779347).

The Gabon study evaluated the UCP-LF-CAA diagnostic test using a set of 3 interlinked prospective, observational sub-studies (A, B, C). Sub-study A, the core trial, evaluated the accuracy of the UCP-LF CAA urine test against a set of other Schistosoma diagnostic tests in a cross-sectional trial design. Sub-study B, an observational follow-up study of sub-study A, included women positive for S haematobium selected to receive PZQ treatment immediately or after delivery followed by weekly sample collection. Data collected in this sub-study will provide further safety data for PZQ administration during pregnancy. Sub-study C, a longitudinal study of 24 months, will determine the incidence of S haematobium infection as well as the age for first infection in infants.

Results from the UCP-LF-CAA test show that egg microscopy underestimates the prevalence of active Schistosoma infections by a factor of 10. The UCP-LF-CAA shows superiority over parasitological methods and is highly sensitive and specific in pregnant women.

“The test can easily identify individuals with very low levels of infection as well as early infections and is well-suited for determining efficacy (or even failure) of treatment,” investigators concluded. While studies are still on-going with sub-Study B and C expected to be finished in 2021 and 2022, respectively, investigators believe “the test is ready to be taken up by industry for upscaling and deployment at a larger scale” based on the results.

Reference

Honkpehedji YJ, Adegnika AA, Dejon-Agobe JN, et al. Prospective, observational study to assess the performance of CAA measurement as a diagnostic tool for the detection of Schistosoma haematobium infections in pregnant women and their child in Lambaréné, Gabon: study protocol of the freeBILy clinical trial in Gabon. BMC Infect Dis. 2020;20(1):718. doi:10.1186/s12879-020-05445-1