Circulating Anodic Antigen (CAA): A Highly Sensitive Diagnostic Biomarker to Detect Active Schistosoma Infections-Improvement and Use during SCORE.

Paul L A M Corstjens,Eugene Ruberanziza,Philip Loverde,Stefanie Knopp,Daniel G Colley,Michelle N Clements,Carl H Campbell,Irenee Umulisa,Thomas Kariuki,Lydia Atkins,Sue Binder,Safari Kinung’Hi,Giuseppina Ortu,Govert J Van Dam,Claudia J De Dood,William Evan Secor,Udo Wittmann

doi:10.4269/ajtmh.19-0819

Abstract

.The Schistosomiasis Consortium for Operational Research and Evaluation (SCORE) was funded in 2008 to conduct research that would support country schistosomiasis control programs. As schistosomiasis prevalence decreases in many places and elimination is increasingly within reach, a sensitive and specific test to detect infection with Schistosoma mansoni and Schistosoma haematobium has become a pressing need. After obtaining broad input, SCORE supported Leiden University Medical Center (LUMC) to modify the serum-based antigen assay for use with urine, simplify the assay, and improve its sensitivity. The urine assay eventually contributed to several of the larger SCORE studies. For example, in Zanzibar, we demonstrated that urine filtration, the standard parasite egg detection diagnostic test for S. haematobium, greatly underestimated prevalence in low-prevalence settings. In Burundi and Rwanda, the circulating anodic antigen (CAA) assay provided critical information about the limitations of the stool-based Kato–Katz parasite egg-detection assay for S. mansoni in low-prevalence settings. Other SCORE-supported CAA work demonstrated that frozen, banked urine specimens yielded similar results to fresh ones; pooling of specimens may be a useful, cost-effective approach for surveillance in some settings; and the assay can be performed in local laboratories equipped with adequate centrifuge capacity. These improvements in the assay continue to be of use to researchers around the world. However, additional work will be needed if widespread dissemination of the CAA assay is to occur, for example, by building capacity in places besides LUMC and commercialization of the assay. Here, we review the evolution of the CAA assay format during the SCORE period with emphasis on urine-based applications.

Highlights

The Schistosomiasis Consortium for Operational Research and Evaluation (SCORE) was funded in 2008 to conduct research to support country programs to control and eliminate schistosomiasis.[1]
As schistosomiasis prevalence decreases in many places and elimination is increasingly within reach, a sensitive and specific test to detect infection with Schistosoma mansoni and Schistosoma haematobium has become a pressing need
The evaluation found that a large number of specimens thought to be negative for S. haematobium infections by urine filtration were found to be positive using this upconverting particles (UCP)-lateral flow (LF) circulating anodic antigen (CAA) assay (Figure 2)

Summary

Introduction

The Schistosomiasis Consortium for Operational Research and Evaluation (SCORE) was funded in 2008 to conduct research to support country programs to control and eliminate schistosomiasis.[1]. This study was the first time that the performance of the high-sensitivity UCAA2000 assay, which used 2 mL of urine, was evaluated for use in a potential schistosomiasis elimination setting and a local laboratory.[34] The evaluation found that a large number of specimens thought to be negative for S. haematobium infections by urine filtration were found to be positive using this UCP-LF CAA assay (Figure 2).

Results

Conclusion