Field evaluations of the Point-of-Care (POC) Circulating Cathodic Antigen (CCA) urine assay for detection of S. mansoni infection
More “field-applicable,” more sensitive and more cost effective screening tools than stool examination by Kato-Katz microscopy are needed to detect S. mansoni infection. This is especially true as programs scale-up and expand NTD integrated national efforts with the additional resources being made available by several donors.
In 2010, the Schistosomiasis Consortium for Operational Research and Evaluation (SCORE) funded a 5-country evaluation of the commercially available Point-of-Care (POC) urine assay for detection of Circulating Cathodic Antigen (CCA) as indication of infection by S. mansoni. Investigators in Cameroon, Ethiopia, Cote d’Ivoire, Kenya and Uganda evaluated both the commercially available POC-CCA assay and a lower sensitivity assay provided by the manufacturer, Rapid Medical Diagnostics. The evaluation was conducted among schoolchildren in areas anticipated to have high, medium and low prevalence and intensities of S. mansoni infection, including some areas with mixed S. mansoni and S. haematobium infection. In addition, children were tested from an area in Ethiopia that was believed to be endemic for soil-transmitted helminths (STH) but non-endemic for S. mansoni.
The CCA antigen is a genus-specific glycan vomited by adult schistosome worms into the blood stream that can be detected in the urine.
Study sites completed data analysis, and publications are listed on the publications page of this website. The SCORE Secretariat and colleagues have completed analysis of the dataset combining results from all of the studies. An open access article was published in the March 2013 issue of The American Journal of Tropical Medicine and Hygiene.
Based on the preliminary study results, SCORE believes that a single urine examination by the commercially available POC-CCA cassette-based test can be used instead of a single stool examination by the Kato-Katz method to assess prevalence of S. mansoni in children of school age. This recommendation has been provided to the World Health Organization.
The work conducted in the 5-country study has led to additional examination of POC-CCA as a useful diagnostic tool. In 2015, a systematic literature review was conducted to investigate the relationship between results from Kato-Katz and POC-CCA. The authors found 25 published papers compare the prevalence of S. mansoni infection by Kato-Katz with that by the POC-CCA. Nineteen of these studies met criteria for data extraction and analysis. The results indicate that below 50% prevalence, POC-CCA is a much more sensitive test than Kato-Katz. However, the existing data are inadequate to precisely define the relationship between POC-CCA and KK at lower levels of KK prevalence. More studies directly comparing the two assays in low prevalence areas are essential to inform decision-making by national schistosomiasis control programs.