Abstract

.Efforts to control Schistosoma mansoni infection depend on the ability of programs to effectively detect and quantify infection levels and adjust programmatic approaches based on these levels and program goals. One of the three major objectives of the Schistosomiasis Consortium for Operational Research and Evaluation (SCORE) has been to develop and/or evaluate tools that would assist Neglected Tropical Disease program managers in accomplishing this fundamental task. The advent of a widely available point-of-care (POC) assay to detect schistosome circulating cathodic antigen (CCA) in urine with a rapid diagnostic test (the POC-CCA) in 2008 led SCORE and others to conduct multiple evaluations of this assay, comparing it with the Kato–Katz (KK) stool microscopy assay—the standard used for more than 45 years. This article describes multiple SCORE-funded studies comparing the POC-CCA and KK assays, the pros and cons of these assays, the use of the POC-CCA assay for mapping of S. mansoni infections in areas across the spectrum of prevalence levels, and the validation and recognition that the POC-CCA, although not infallible, is a highly useful tool to detect low-intensity infections in low-to-moderate prevalence areas. Such an assay is critical, as control programs succeed in driving down prevalence and intensity and seek to either maintain control or move to elimination of transmission of S. mansoni.

Highlights

  • The microscopy-based Kato–Katz (KK) thick smear fecal assay is highly specific and has been used widely for more than 45 years[1] to determine the prevalence and gauge the intensity of Schistosoma mansoni infections

  • As prevalence has decreased in many places because of preventive chemotherapy with praziquantel (PZQ), it has become increasingly apparent that Neglected Tropical Disease (NTD) program managers need a more sensitive and more field-applicable assay for mapping S. mansoni infection than stool microscopy

  • Further evaluation of the POC-cathodic antigen (CCA) test was included in the Schistosomiasis Consortium for Operational Research and Evaluation (SCORE) proposal to the Bill & Melinda Gates Foundation (BMGF) because of the potential for this assay to be an important tool for mapping S. mansoni infections

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Summary

INTRODUCTION

The microscopy-based Kato–Katz (KK) thick smear fecal assay is highly specific and has been used widely for more than 45 years[1] to determine the prevalence and gauge the intensity of Schistosoma mansoni infections. The price per cassette was higher than that of the materials used to perform the KK In another SCORE study, once all of the expenditures were considered, including the additional personnel time and return field visits required by KK, the two tests were found to be comparable in cost.[15] By the time of this writing in 2019, the cost of the POC-CCA assay has decreased even further because of its more widespread use and purchases in bulk. SCORE undertook several additional studies in Kenya related to POC-CCA assay performance to expand the database and further establish the rationale for its use to map S. mansoni infections. These assessments found no significant variability among the batches of the assays that they studied at that time, and that intra- and inter-reader variability was insignificant. SCORE-SUPPORTED MAPPING STUDIES COMPARING THE POC-CCA ASSAY WITH THE KK ASSAY FOR MAPPING

IN LOW TO VERY LOW PREVALENCE AREAS
Treatment history in the area
Findings
OTHER SCORE EFFORTS RELATED TO DIAGNOSTIC TOOLS
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