title: Evaluation and optimization of the Circulating Cathodic Antigen (POC-CCA) cassette test for detectingSchistosoma mansoniinfection by using image analysis in school children in Mwanza Region, Tanzania.
abstract: There is a need for diagnostic techniques which are sensitive, specific, rapid and easy to perform at the point-of-care. The aim of this study was to evaluate the diagnostic performance of the Circulating Cathodic Antigen (POC-CCA) assay forSchistosoma mansoniin four schools along the coast of Lake Victoria in Mwanza Region, Tanzania, and to optimize the reading of the POC-CCA test lines by using a computer software image analysis. Initially, a pilot study in 106 school children indicated that time of urine collection did not have an impact on CCA results as 84.9% (90) had identical scores from a urine collected in the morning and a urine taken at midday after drinking 0.5 L of water. The main study was conducted among 404 school children (aged 9-12 years) where stool and urine samples were collected for three consecutive days. ForS. mansonidiagnosis, stool samples were examined for eggs with duplicate Kato-Katz smears, whereas urine samples were tested for presence of antigen by POC-CCA. The proportion of positive individuals forS. mansoniby one POC-CCA was higher compared to two Kato-Katz smears (66.1% vs. 28.7%; p < 0.0001). Both proportions increased expectedly when three POC-CCAs were compared to six Kato-Katz smears (75.0% vs. 42.6%; p < 0.0001). Three POC-CCAs were more sensitive (94.7%) than six Kato-Katz smears (53.8%) using the combined results of three POC-CCAs and six Kato-Katz smears as the 'gold standard'. To optimize the reading of the POC-CCA, a Software tool (Image Studio Lite®) was used to read and quantify the colour (expressed as pixels) of the test line on all positive tests, showing a positive correlation between number of pixels and the visually scored intensities and between number of pixels and egg counts. In conclusion, the POC-CCA assay seems to be a more appropriate tool forS. mansonidiagnosis compared to the Kato-Katz method in endemic communities such as Mwanza Region. Optimization of the tool in terms of cassette-reading could be assessed by computer software which was able to quantify the colour of the lines in the strip of the cassette.
authors.affiliation: Parasitology and Aquatic Diseases, Department of Veterinary Disease Biology, University of Copenhagen, Dyrlaegevej 100, DK-1870 Frederiksberg C, Denmark.
authors.forename: Miriam
authors.initials: M
authors.lastname: Casacuberta
authors.affiliation: National Institute for Medical Research (NIMR), Mwanza Research Centre, Mwanza, Tanzania).
authors.forename: Safari
authors.initials: S
authors.lastname: Kinunghi
authors.affiliation: Parasitology and Aquatic Diseases, Department of Veterinary Disease Biology, University of Copenhagen, Dyrlaegevej 100, DK-1870 Frederiksberg C, Denmark.
authors.forename: Birgitte J
authors.initials: BJ
authors.lastname: Vennervald
authors.affiliation: Parasitology and Aquatic Diseases, Department of Veterinary Disease Biology, University of Copenhagen, Dyrlaegevej 100, DK-1870 Frederiksberg C, Denmark.
authors.forename: Annette
authors.initials: A
authors.lastname: Olsen
keywords: CCA; Computer image analyses; Schistosoma mansoni; School children; Tanzania