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. 2011 Jan 25;5(1):e951.
doi: 10.1371/journal.pntd.0000951.

Evaluation of urine CCA assays for detection of Schistosoma mansoni infection in Western Kenya

Hillary L Shane  1 , Jennifer R Verani, Bernard Abudho, Susan P Montgomery, Anna J Blackstock, Pauline N M Mwinzi, Sara E Butler, Diana M S Karanja, W Evan Secor
Affiliations

Evaluation of urine CCA assays for detection of Schistosoma mansoni infection in Western Kenya

Hillary L Shane et al. PLoS Negl Trop Dis. .

Abstract

Although accurate assessment of the prevalence of Schistosoma mansoni is important for the design and evaluation of control programs, the most widely used tools for diagnosis are limited by suboptimal sensitivity, slow turn-around-time, or inability to distinguish current from former infections. Recently, two tests that detect circulating cathodic antigen (CCA) in urine of patients with schistosomiasis became commercially available. As part of a larger study on schistosomiasis prevalence in young children, we evaluated the performance and diagnostic accuracy of these tests--the carbon test strip designed for use in the laboratory and the cassette format test intended for field use. In comparison to 6 Kato-Katz exams, the carbon and cassette CCA tests had sensitivities of 88.4% and 94.2% and specificities of 70.9% and 59.4%, respectively. However, because of the known limitations of the Kato-Katz assay, we also utilized latent class analysis (LCA) incorporating the CCA, Kato-Katz, and schistosome-specific antibody results to determine their sensitivities and specificities. The laboratory-based CCA test had a sensitivity of 91.7% and a specificity of 89.4% by LCA while the cassette test had a sensitivity of 96.3% and a specificity of 74.7%. The intensity of the reaction in both urine CCA tests reflected stool egg burden and their performance was not affected by the presence of soil transmitted helminth infections. Our results suggest that urine-based assays for CCA may be valuable in screening for S. mansoni infections.

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Conflict of interest statement

The authors have declared that no competing interests exist.

Figures

Figure 1
Figure 1. Prevalence of schistosome positive individuals by age.
Prevalence increases with age for all 4 assays.
Figure 2
Figure 2. STH infection status does not affect SWAP-ELISA values.
Comparison of SWAP ELISA values in schistosome negative (top) and schistosome infected (bottom) individuals based on STH infection status. Y-axis scales differ in order to better analyze the schistosome negative individuals. There are no significant difference between SWAP ELISA values based on STH infection status (p = 0.4263 and 0.8868, respectively) with one-way analysis of variance (Kruskal-Wallis ANOVA).
Figure 3
Figure 3. SWAP-ELISA values correlate with level of schistosome infection.
Average SWAP-ELISA values for the negative, light, moderate and heavy intensities of infection as determined by average EPG (p<0.001, Kruskal-Wallis ANOVA).
Figure 4
Figure 4. CCA assay band intensity correlates with level of schistosome infection.
The intensity of the results of the CCA assays are associated with schistosome infection intensity (p<0.0001, Kruskal-Wallis ANOVA), as determined by the Kato-Katz method (EPG).
See this image and copyright information in PMC

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