Rapid diagnosis of schistosomiasis by antigen detection in urine with a reagent strip

Abstract

For the rapid and simple diagnosis of schistosomiasis, a reagent strip assay for detection of circulating cathodic antigen (CCA) in urine was developed. The test was based on a previously developed sandwich enzyme- linked immunosorbent assay (ELISA) using a combination of two anti-CCA monoclonal antibodies. For the reagent strip assay, as the capture matrix, monoclonal antibody was coated onto a nitrocellulose membrane and mounted on polyvinyl chloride strips. Urine samples were then tested in an assay consisting of a combined incubation step of the urine sample and biotinylated detecting antibody followed by incubation in streptavidin peroxidase and a subsequent staining. The specificity and the sensitivity of the assay, as determined with urine samples of 61 uninfected controls and 67 Schistosoma mansoni-infected individuals, were 96.7 and 95.5%, respectively. The results of the reagent strip assay compared very well with microscopical parasitological diagnosis by the standard Kato-Katz method for the same individuals. The reagent strip test has a lower detection limit of 1 ng of CCA per ml and can be completed in 75 min. By the inclusion of two reference bands on the strips, standardized reading could be achieved. This reagent strip assay is a promising tool for qualitative diagnosis of S. mansoni infections in control programs.