A new diagnostic strategy which uses a luminol-H2O2 system to detect helminth eggs in fecal sediments processed by the Helmintex method

Schistosomiasis remains a serious public health problem in tropical regions, affecting more than 250 million people. Sensitive diagnostic methods represent key tools for disease elimination, in particular in areas with low endemicity. Advances in the use of luminol-based chemiluminescent techniques have enabled greater sensitivity and speed in obtaining results in different diagnostic settings. In this study, we developed a luminol-H2O2 chemiluminescence (CL) method to detect Schistosoma mansoni eggs in human fecal sediments processed by the Helmintex (HTX) method. After S. mansoni eggs were incubated with a solution of luminol-H2O2 the light emission was detected and measured by spectrophotometry at 431 nm for 5 min, using detection and counts of eggs by bright field optical microscopy as a reference. CL intensity was found to correlate with different sources and numbers of eggs. Furthermore, our results showed that the CL method can distinguish positive from negative samples with 100% sensitivity and 71% specificity. To our knowledge, this is the first study to report the use of CL for the diagnosis of helminths from fecal samples. The combination of the HTX method with CL represents an important advance in providing a reference method with the highest standards of sensitivity

Low specificity of point-of-care circulating cathodic antigen (POC sbnd CCA) diagnostic test in a non-endemic area for schistosomiasis mansoni in Brazil

This work was funded by the Secretaria de Vigilância em Saúde / Fundo Nacional de Saúde / Ministério da Saúde (SVS/FNS/MS) - [TED/FNS: 118/2017; SIAFI: 691919/25000.479741/2017–05].Universidade Federal do Espírito Santo. Center for Health Sciences. Infectious Diseases Unit. Vitória, ES, Brazil / Pontifícia Universidade Católica do Rio Grande do Sul. School of Sciences. Research Group on Biomedical Parasitology. Porto Alegre, RS, Brazil.Pontifícia Universidade Católica do Rio Grande do Sul. School of Sciences. Research Group on Biomedical Parasitology. Porto Alegre, RS, Brazil.Pontifícia Universidade Católica do Rio Grande do Sul. School of Sciences. Research Group on Biomedical Parasitology. Porto Alegre, RS, Brazil.Pontifícia Universidade Católica do Rio Grande do Sul. School of Sciences. Research Group on Biomedical Parasitology. Porto Alegre, RS, Brazil.Pontifícia Universidade Católica do Rio Grande do Sul. School of Sciences. Research Group on Biomedical Parasitology. Porto Alegre, RS, Brazil.Pontifícia Universidade Católica do Rio Grande do Sul. School of Sciences. Research Group on Biomedical Parasitology. Porto Alegre, RS, Brazil.Universidade Federal do Ceará. Department of Clinical and Toxicological Analyses. Fortaleza, CE, Brazil.Fundação Oswaldo Cruz. René Rachou Institute. Belo Horizonte, MG, Brazil.Ministério da Saúde. Secretaria de Vigilância em Saúde. Instituto Evandro Chagas. Ananindeua, PA, Brasil.Fundação Oswaldo Cruz. Oswaldo Cruz Institute. Rio de Janeiro, RJ, Brazil.Fundação Oswaldo Cruz. René Rachou Institute. Belo Horizonte, MG, Brazil.Fundação Oswaldo Cruz. Gonçalo Muniz Institute. Salvador, BA, Brazil.Fundação Oswaldo Cruz. Gonçalo Muniz Institute. Salvador, BA, Brazil / Federal University of Bahia. Faculty of Medicine of Bahia. Salvador, BA, Brazil / Yale University. School of Public Health. Department of Epidemiology of Microbial Diseases. New Haven, CT, United States of America.Fundação Oswaldo Cruz. Oswaldo Cruz Institute. Rio de Janeiro, RJ, Brazil.A point-of-care test for detecting schistosome circulating cathodic antigen in urine (POC sbnd CCA) has been proposed for mapping infection and defining prevalence thresholds for mass drug administration (MDA). However, there is increasing evidence that POC[sbnd]CCA may yield false-positive results, which requires rigorous specificity evaluation in non-endemic areas. POC[sbnd]CCA was applied in an area known to be free from infection and devoid of any condition for schistosomiasis transmission as part of a multicentre study to evaluate the performance of POC[sbnd]CCA in Brazil's low or potentially endemic settings. Besides POC[sbnd]CCA detection in urine, a search for eggs in stool was performed by Kato-Katz (KK) and Helmintex (HTX) methods. One-hundred-and-seventy-four participants returned urine samples, 140 of which delivered stool samples. All these were HTX-negative for Schistosoma mansoni, and all 118 tested with KK were negative for both S. mansoni and soil-transmitted helminths. POC[sbnd]CCA results from freshly collected urine yielded a specificity of 62.1% (95% CI: 53.6% - 70.2%), taking trace outcomes as positive according to the manufacturer's instructions. Retesting urine from the 140 HTX-negatives after one-year storage at -20 °C with two new POC[sbnd]CCA batches simultaneously yielded significantly different specificities (34.3%; 95%CI: 26.5% – 42.8% and 75.0%; 95% CI: 67.0% - 81.9%). These two batches had a weak agreement (Cohen's kappa: 0.56; 95%CI: 0.44–0.68) among the 174 urine samples retested. At present, POC[sbnd]CCA cannot be recommended either as a cut-off point for MDA or a reliable diagnostic tool for treatment of the infection carriers (selective chemotherapy) in low endemic areas and at final stages of transmission interruption. Manufacturers should be required to optimize production standardization and to assure quality and reproducibility of the test. Extended rigorous performance evaluations by different users from different regions are needed before POC[sbnd]CCA is widely recommende