Enhanced detection of Schistosoma circulating antigens by testing 1 ml urine samples using immunomagnetic beads

The potential advantage of increasing the sample volume for enhanced detection of two Schistosoma circulating antigens in urine has been evaluated. Two different, monoclonal antibody based, immunomagnetic beads assays detecting circulating anodic antigen (CAA) and circulating soluble egg antigen (CSEA), respectively, were investigated. By increasing the sample volume to 1.0 ml, the lower detection limit of antigen dilution series was improved six–eight-fold in both immunomagnetic beads assays. Indeed, an improvement could be shown when testing the urine of Schistosoma-infected individuals with these magnetic beads assays. To compare the sensitivity of the immunomagnetic beads method with the standard ELISA, urine was experimentally adjusted to mirror low natural infection intensities. CSEA-positive urine samples were adjusted to levels below the detection limit of the corresponding ELISA and indeed were still found positive by the CSEA immunomagnetic beads assay. These results demonstrate that by using immunomagnetic beads, an assay method which can utilise larger sample volumes than an ELISA, enhanced detection can be achieved. This might be particularly valuable in areas with low prevalence of schistosomiasis or for the assessment of cure after chemotherapy.