Original Research ARTICLE
Performance of an Ultra-Sensitive Assay Targeting the Circulating Anodic Antigen (CAA) for Detection of Schistosoma mansoni Infection in a Low Endemic Area in Brazil
- 1Faculty of Medicine, Federal University of Ceará, Brazil
- 2Leiden University Medical Center, Netherlands
- 3Institute of Microbiology, Federal University of Rio de Janeiro, Brazil
- 4Universidade Federal Fluminense, Brazil
Techniques with high sensitivity and specificity are required for an accurate diagnosis in low-transmission settings, where the conventional parasitological methods are insensitive. We determined the accuracy of an up-converting phosphor-lateral flow circulating anodic antigen (UCP-LF CAA) assay in urine and serum for Schistosoma mansoni diagnosis in low-prevalence settings in Ceará, Brazil, before and after praziquantel treatment. Clinical samples of a total of 258 individuals were investigated by UCP-LF CAA, point-of-care - circulating cathodic antigen (POC-CCA), soluble worm antigen preparation (SWAP)-ELISA and Kato-Katz (KK); a selection of 128 stools by real-time PCR technique. Three and 6-weeks after treatment, samples were collected and evaluated by detection Schistosoma circulating antigens (CAA and CCA). The UCP-LF CAA assays detected 80 positives (31%) with urine and 82 positives (31.8%) with serum. The urine POC-CCA and serum SWAP-ELISA assays detected 30 (11.6%) and 107 (40.7%) positives, respectively. The Kato-Katz technique revealed only 4 positive stool samples (1.6%). Among the 128 individuals with complete data records, 19 cases were identified by PCR (14.8%); Sensitivities and specificities of the UCP-LF CAA assays, determined versus a combined reference standard based on CCA/KK/PCR positivity, ranged from 60-68% and 68-77%, respectively. In addition only for comparative purposes, sensitivities of the different assays were determined versus a comparative reference based on CAA/KK/PCR positivity, showing the highest sensitivity for the urine CAA assay (80%), followed by the serum CAA (70.9%), SWAP-ELISA (43.6%), PCR (34.5%), POC-CCA (29.1%), whilst triplicate Kato-Katz thick smears had a very low sensitivity (3.6%). CAA concentrations were higher in serum than in urine and were significantly correlated. There was a significant decrease in urine and serum CAA levels 3 and 6-weeks after treatment. The UCP-LF CAA assays revealed 33 and 28 S. mansoni-infected patients at the 3- and 6-week posttreatment follow-up, respectively. The UCP-LF CAA assays show high sensitivity for the diagnosis of S. mansoni in low-endemicity settings. It detects a considerably higher number of infections than microscopy, POC-CCA or PCR. Also it shows to be very useful for evaluating cure rates after treatment. Hence, the UCP-LF CAA assay is a robust and promising diagnostic approach in low-transmission settings.
Keywords: Circulating anodic antigen (CAA), diagnosis, Up-converting phosphor lateral-flow assay, POC-CCA test, Polymerase chain reaction (PCR), Schistosoma mansoni, Brazil, Low endemic area
Received: 20 Sep 2018;
Accepted: 13 Mar 2019.
Edited by:Thiago Almeida Pereira, Institute for Stem Cell Biology and Regenerative Medicine, Stanford University, United States
Reviewed by:Deborah Negrão-Corrêa, Federal University of Minas Gerais, Brazil
Edward Oliveira, Fiocruz Research Center Renê Rachou, Brazil
Copyright: © 2019 Sousa, van Dam, Pinheiro, de Dood, Peralta, Peralta, Daher, Corstjens and Bezerra. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.
Dr. Govert J. van Dam, Leiden University Medical Center, Leiden, 2333, Netherlands, email@example.com
Prof. Fernando Schemelzer M. Bezerra, Faculty of Medicine, Federal University of Ceará, Fortaleza, Brazil, firstname.lastname@example.org