Background Schistosomiasis is caused by infection with parasitic worms, schistosomes, and affects hundreds of millions people worldwide. The detection of schistosome circulating cathodic and anodic antigens (CCA and CAA) has proven to be highly valuable in diagnosing intestinal and urinary schistosomiasis. Within the freeBILy project, a CCA/CAA duplex test was developed which detects both antigens simultaneously to improve the diagnostic accuracy and potentially identify Schistosoma spp based on CAA/CCA ratios.

Methods CAA and CCA were incorporated into the current laboratory-based UCP-LF test platform utilizing a duplex test-format; i.e. a single prototype device with two parallel lateral flow (LF) strips. Test performance was evaluated using banked sample sets (serum and urine) from two different Schistosoma endemic areas using standardized protocols. Samples were available from both cross-sectional as well as school-age children based population studies. In a subset, CCA/CAA ratios were determined.

Results CAA-levels in urine were lower compared to CAA-levels in serum, both for S. mansoni (Sm) and S. haematobium (Sh). Significantly more CCA was observed in Sm urines compared to Sh urines. In urine the CCA/CAA ratio for Sm was significantly higher compared to the CAA/CCA ratio for Sh, while no differences were observed in serum. Species could not be identified unequivocally based on the CCA/CAA ratio.

Conclusion Combined detection of CAA and CCA improved diagnostic accuracy and showed added value compared to detection either antigen separately, particularly in Sh settings where the POC-CCA performance is limited. Identification of Schistosoma species based on the CCA/CAA ratio seems challenging due to multiple factors. Generally, CAA and CCA levels in serum and urine show marked differences which would benefit from further focused in-depth studies.