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      The use of the circulating cathodic antigen (CCA) urine cassette assay for the diagnosis and assessment of cure of Schistosoma mansoni infections in an endemic area of the Amazon region

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          Abstract

          INTRODUCTION

          Schistosomiasis is a poverty-related disease that affects people in 78 countries worldwide. This study aimed to evaluate the point-of-care circulating cathodic antigen (POC-CCA) test performance using sensitive parasitological methods as a reference standard (RS) in individuals before and after treatment.

          METHODS

          The RS was established by combining the results of 16 Kato-Katz slides and the Helmintex ® method. Positivity rates of the POC-CCA test and Kato-Katz and Helmintex ® methods were calculated before treatment and 30 days afterward. Furthermore, the sensitivity, specificity, accuracy, and kappa coefficient before treatment were determined by comparing the methods. The cure rate was defined 30 days after treatment.

          RESULTS

          Among the 217 participants, the RS detected a total of 63 (29.0%) positive individuals. The POC-CCA test identified 79 (36.4%) infections. The evaluation of POC-CCA test performance in relation to the RS revealed a sensitivity of 61.9%, specificity of 74.0%, accuracy of 70.5%, and kappa coefficient of 0.33. Out of the 53 remaining participants after treatment, a total of 45 (81.1%) showed egg negative results, and 8 (18.9%) were egg positive according to the RS. A total of 5 (9.4%) egg-positive and 37 (69.8%) egg-negative individuals were positive by the POC-CCA test.

          CONCLUSIONS

          Our data show that the POC-CCA test has potential as an auxiliary tool for the diagnosis of Schistosoma mansoni infection, yielding better results than 16 Kato-Katz slides from three different stool samples. However, the immunochromatographic test lacks sufficient specificity and sensitivity for verifying the cure rate after treatment.

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          Underestimation of Schistosoma mansoni prevalences.

          Field methods used for detecting Schistosoma mansoni infection miss a certain proportion of the infections. Prevalences of infection appear to be far under-estimated by faecal screening, with important consequences for control and research. Sake de Vlos and Bruno Gryseels investigate how the number of undetected infections can be statistically inferred from population surveys.
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            Underestimation of Schistosoma mansoni prevalences

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              Study of diagnostic accuracy of Helmintex, Kato-Katz, and POC-CCA methods for diagnosing intestinal schistosomiasis in Candeal, a low intensity transmission area in northeastern Brazil

              Control initiatives have successfully reduced the prevalence and intensity of schistosomiasis transmission in several localities around the world. However, individuals that release low numbers of eggs in their feces may not be detected by classical methods that are limited by low sensitivity. Given that accurate estimates of prevalence are key to implementing planning control actions for the elimination of schistosomiasis, new diagnostic tools are needed to effectively monitor infections and confirm transmission interruption. The World Health Organization recommends the Kato-Katz (KK) thick smear as a parasitological test for epidemiological surveys, even though this method has been demonstrated to underestimate prevalence when egg burdens are low. The point-of-care immunodiagnostic for detecting schistosome cathodic circulating antigen (POC-CCA) method has been proposed as a more sensitive substitute for KK in prevalence estimations. An alternative diagnostic, the Helmintex (HTX) method, isolates eggs from fecal samples with the use of paramagnetic particles in a magnetic field. Here, a population-based study involving 461 individuals from Candeal, Sergipe State, Brazil, was conducted to evaluate these three methods comparatively by latent class analysis (LCA). The prevalence of schistosomiasis mansoni was determined to be 71% with POC-CCA, 40.% with HTX and 11% with KK. Most of the egg burdens of the individuals tested (70%) were < 1 epg, thereby revealing a dissociation between prevalence and intensity in this locality. Therefore, the present results confirm that the HTX method is a highly sensitive egg detection procedure and support its use as a reference method for diagnosing intestinal schistosomiasis and for comparative evaluation of other tests.
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                Author and article information

                Journal
                Rev Soc Bras Med Trop
                Rev. Soc. Bras. Med. Trop
                rsbmt
                Revista da Sociedade Brasileira de Medicina Tropical
                Sociedade Brasileira de Medicina Tropical - SBMT
                0037-8682
                1678-9849
                25 September 2020
                2020
                : 53
                : e20190562
                Affiliations
                [1 ]Universidade do Estado do Pará, Programa de Pós-Graduação Strictu Sensu em Biologia Parasitária na Amazônia, Belém, PA, Brasil.
                [2 ]Instituto Evandro Chagas/SVS/MS, Laboratório de Parasitoses Intestinais, Esquistossomose e Malacologia, Secção de Parasitologia, Ananindeua, PA, Brasil.
                [3 ]Pontifícia Universidade Católica do Rio Grande do Sul, Programa de Pós-Graduação em Medicina e Ciências da Saúde, Laboratório de Parasitologia Biomédica, Porto Alegre, RS, Brasil.
                [4 ]Universidade Federal de Minas Gerais, Departamento de Parasitologia, Belo Horizonte, MG, Brasil.
                Author notes
                Corresponding author: Msc. Sergei Rodrigo Magalhães de Sousa . e-mail: rodrigo.bio.uepa@ 123456gmail.com

                Authors’ contributions: MJE and SMG participated in the design of the study. SRMS, IHLD, ÁLSF, VF, JFNC, and MJE participated in the acquisition, analysis, and interpretation of data and drafting of the manuscript. All authors read and approved the final manuscript.

                Conflict of interest: The authors declare that they have no competing interests.

                Author information
                http://orcid.org/0000-0003-2197-7323
                Article
                00348
                10.1590/0037-8682-0562-2019
                7523523
                32997046
                cd484d98-5c3a-4478-afc0-baca5e71ddd5

                This is an open-access article distributed under the terms of the Creative Commons Attribution License

                History
                : 07 February 2020
                : 20 July 2020
                Page count
                Figures: 1, Tables: 4, Equations: 0, References: 29
                Categories
                Major Article

                schistosoma mansoni,kato-katz,helmintex®,poc-cca,treatment
                schistosoma mansoni, kato-katz, helmintex®, poc-cca, treatment

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