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Open Access Short report

Performance of circulating cathodic antigen (CCA) urine-dipsticks for rapid detection of intestinal schistosomiasis in schoolchildren from shoreline communities of Lake Victoria

CJ Standley12, NJS Lwambo3, CN Lange4, HC Kariuki5, M Adriko6 and JR Stothard1*

Author Affiliations

1 Biomedical Parasitology Division, Department of Zoology, Natural History Museum, Cromwell Road, SW7 5BD, London, UK

2 Institute of Genetics, School of Biology, University of Nottingham, NG7 2RD, Nottingham, UK

3 National Institute for Medical Research, Mwanza, Tanzania

4 Invertebrate Zoology Section, Nairobi National Museum, Museum Hill, P.O. Box 40658, Nairobi, Kenya

5 Division of Vector Borne Diseases, Ministry of Health, Nairobi, Kenya

6 Vector Control Division, Ministry of Health, Kampala, Uganda

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Parasites & Vectors 2010, 3:7  doi:10.1186/1756-3305-3-7

Published: 5 February 2010

Abstract

For disease surveillance and mapping within large-scale control programmes, RDTs are becoming popular. For intestinal schistosomiasis, a commercially available urine-dipstick which detects schistosome circulating cathodic antigen (CCA) in host urine is being increasingly applied, however, further validation is needed. In this study, we compared the CCA urine-dipstick test against double thick Kato-Katz faecal smears from 171 schoolchildren examined along the Tanzanian and Kenyan shorelines of Lake Victoria. Diagnostic methods were in broad agreement; the mean prevalence of intestinal schistosomiasis inferred by Kato-Katz examination was 68.6% (95% confidence intervals (CIs) = 60.7-75.7%) and 71.3% (95% CIs = 63.9-78.8%) by CCA urine-dipsticks. There were, however, difficulties in precisely 'calling' the CCA test result, particularly in discrimination of 'trace' reactions as either putative infection positive or putative infection negative, which has important bearing upon estimation of mean infection prevalence; considering 'trace' as infection positive mean prevalence was 94.2% (95% CIs = 89.5-97.2%). A positive association between increasing intensity of the CCA urine-dipstick test band and faecal egg count was observed. Assigning trace reactions as putative infection negative, overall diagnostic sensitivity (SS) of the CCA urine-dipstick was 87.7% (95% CIs = 80.6-93.0%), specificity (SP) was 68.1% (95% CIs = 54.3-80.0%), positive predictive value (PPV) was 86.1% (95% CIs = 78.8-91.7%) and negative predictive value (NPV) was 71.1% (95% CIs = 57.2-82.8%). To assist in objective defining of the CCA urine-dipstick result, we propose the use of a simple colour chart and conclude that the CCA urine-dipstick is a satisfactory alternative, or supplement, to Kato-Katz examination for rapid detection of intestinal schistosomiasis.