Accuracy of the urine point-of-care circulating cathodic antigen assay for diagnosing Schistosomiasis mansoni infection in Brazil: A multicenter study

ABSTRACT Background: The World Health Organization recommends a market-ready, urine-based point-of-care diagnostic test for circulating cathodic antigens (CCA) to determine the prevalence of S. mansoni. This study evaluated the performance of the URINE CCA (SCHISTO) ECO TESTE® (POC-ECO), which is currently available in Brazil. Methods: Residents from eight sites with different prevalence estimates provided one urine sample for POC-ECO and one stool sample for Kato-Katz (KK) and Helmintex® (HTX) testing as an egg-detecting reference for infection status. Results: None of the study sites had significantly higher POC-ECO accuracy than KK. Conclusions: POC-ECO is not currently recommended in Brazilian schistosomiasis elimination programs.

Reliability of point-of-care circulating cathodic antigen assay for diagnosing schistosomiasis mansoni in urine samples from an endemic area of Brazil after one year of storage at -20 degrees Celsius

ABSTRACT Background The World Health Organization recommends reliable point-of-care (POC) diagnostic testing to eliminate schistosomiasis. Lateral flow immunoassay that detects schistosome circulating cathodic antigen (CCA) in urine to establish prevalence thresholds for intervention in endemic areas is recommended. Stored urine may be useful if surveying at-risk populations is delayed or interrupted by unforeseen circumstances, such as the current COVID-19 pandemic. This study evaluated the manufacturer's claim that Schistosoma mansoni infection can be reliably diagnosed in urine samples stored at -20°C for one year. Methods Two-hundred-forty-two subjects from an endemic site in Brazil provided one urine sample each for testing with URINE CCA (SCHISTO) ECO TESTE® (POC-ECO) and one stool sample each for testing with Kato-Katz (KK) and Helmintex® (HTX) as a robust reference standard for infection status. At least 2 ml of urine from each participant was stored at -20°C; after one year, 76 samples were randomly selected for POC-ECO retesting. Results: The POC-ECO agreement between freshly collected and stored urine was inadequate considering trace results as positive (Cohen's kappa coefficient κ = 0.08) and negative (κ = 0.36). POC-ECO accuracy was not significantly greater than that of routine KK (54%; 95% confidence interval: 42.1%-65.5%). Conclusions The precision and accuracy of POC-ECO have to be optimized in both freshly collected and stored urine before it can be recommended for use in control programs in Brazil.

Epidemiology and predictors of occurrence of SCHISTOSOMA MANSONI infection in a low-endemicity area in northeast Brazil

In Latin America 96% of the cases of schistosomiasis occur in Brazil in low-socioeconomic status populations. The epidemiological characteristics and occurrence predictors of Schistosoma mansoni infection were determined in the Bananeiras community, located in Capistrano, a town in Ceará state, Brazil. Sanitary, environmental, socioeconomic, and behavioral data were collected using a semi-structured questionnaire. An investigation to assess S. mansoni infection was conducted using the Kato-Katz and Point-of-Care Circulating Cathodic Antigen (POC-CCA) methods. From the 258 subjects were analyzed, 54.3% (n=140) were women, median age 30 years. Thirty-three (12.8%) individuals were positive by either egg- and/or CCA-positivity. The highest positivity rate was found in the 30-39 year old group. There was no piped water supply, sewage network or municipal refuse collection service. Most individuals were illiterate or had not finished elementary school (66.3%). About 29.1% of the families had a monthly income below one Brazilian minimum wage and 91.1% reported contact with natural water sources. We found an association between infection and age group of 20-40 years, illiteracy, household with 7 inhabitants or more, household with up to 3 rooms and an outhouse. Contrarily, being 40 years old or older and household with up to 6 inhabitants were not risk factors. Schistosomiasis remains a public health problem in this municipality, evidencing a strong association with low socioeconomic conditions and high vulnerability. These findings reinforce the importance of identifying the factors associated with the infection for more effective guidance in actions in control programs targeting schistosomiasis prevention and control.

A conventional polymerase chain reaction-based method for the diagnosis of human schistosomiasis in stool samples from individuals in a low-endemicity area

The aim of this study was to evaluate the efficacy of a polymerase chain reaction (PCR)-based method to detect Schistosoma mansoni DNA in stool samples from individuals living in a low-endemicity area in Brazil. Of the 125 initial stool samples, 80 were ELISA reactive and eggs were identified in 19 of the samples by parasitological examination. For the PCR evaluations, 56 stool samples were selected and divided into five groups. Groups I-IV were scored negative for S. mansoni eggs by parasitological examination. Groups I and II were ELISA reactive, whereas Groups III and IV were ELISA nonreactive. Groups II and III were positive for other intestinal parasites. PCR testing scored eight samples as positive from these four groups. Group V represented the S. mansoni -positive group and it included ELISA-reactive samples that were scored positive for S. mansoni by one or more parasitological examinations (6/19 were positive by Kato-Katz method, 9/17 by saline gradient and 10/13 by Helmintex®). PCR scored 13 of these 19 samples as positive for S. mansoni . We conclude that while none of these methods yielded 100% sensitivity, a combination of techniques should be effective for improving the detection of S. mansoni infection in low-endemicity areas.

The combination of three faecal parasitological methods to improve the diagnosis of schistosomiasis mansoni in a low endemic setting in the state of Ceará, Brazil

Laboratory diagnosis of intestinal schistosomiasis mansoni can be accomplished through various methods of stool examination to detect parasites, ranging from the most classic tests (Kato-Katz) to several methods that are still undergoing validation. This study was conducted to assess two new parasite identification methods for diagnosing schistosomiasis mansoni in residents of a low endemic area in the municipality of Maranguape, in the state of Ceará, Brazil using the Kato-Katz method as a reference and serology (enzyme-linked immunosorbent assay) for the screening of patients. The Kato-Katz, the saline gradient method and the Helmintex® method parasite identification methods were employed only in subjects who exhibited positive serologic tests. The test results were then analysed and treatment of positive individuals was subsequently performed. After comparing the test results, we observed that the saline gradient method and the Helmintex® method were more effective in diagnosing schistosomiasis mansoni in the study area compared with the Kato-Katz method.

Increased detection of schistosomiasis with Kato-Katz and SWAP-IgG-ELISA in a Northeastern Brazil low-intensity transmission area / Aumento da detecção da esquistossomose com Kato-Katz e SWAP-IgG-ELISA, em área de baixa endemicidade, no nordeste do Brasil

INTRODUCTION: The laboratory diagnosis of schistosomiasis is based mainly on the detection of parasite eggs in stool samples through the Kato-Katz (KK) technique, reading one slide by test. However, a widely known limitation of parasitological methods is reduced sensitivity, particularly in low endemic areas. METHODS: To increase sensitivity, we conducted further slide readings from the same stool sample using the parasitological method associated with a serological test. We used the KK method (three slides) and the IgG anti-Schistosoma mansoni-enzyme-linked immunosorbent assay (ELISA) technique to diagnose schistosomiasis in low endemic areas in the Brazilian State of Ceará. Fecal samples and sera from 250 individuals were analyzed. RESULTS: Sixteen percent and 47.2% of samples were positive in parasitological tests and serological tests, respectively. Parasitological methods showed that 32 (80%) individuals tested positive on the first slide, 6 (15%) on the second slide, and 2 (5%) on the third. The performance of the ELISA test in the diagnosis, using the KK method as diagnostic reference, showed a negative predictive value of 100%, with specificity and positive predictive values of 62.8% and 33.9%, respectively. CONCLUSIONS: In this study, the increase from one to three slides analyzed per sample using the KK technique was shown to be a useful procedure for increasing the diagnostic sensitivity of this technique.

INTRODUÇÃO: O diagnóstico laboratorial da esquistossomose é baseada principalmente na detecção de ovos do parasito nas fezes, realizada pela técnica de Kato-Katz (KK), com a leitura de uma lâmina por teste. No entanto, uma limitação conhecida dos métodos coproscópicos é a reduzida sensibilidade, especialmente nas áreas de baixa endemicidade. MÉTODOS: A fim de reduzir essa limitação, realizamos mais leituras da mesma amostra de fezes pelo método coproscópico e associamos a um teste sorológico.Utilizamos o método de KK (três lâminas) e a técnica de IgG-ELISA, buscando aumentar a sensibilidade do diagnóstico da esquistossomose em área de baixa endemicidade, no Estado Brasileiro do Ceará. Amostras de fezes e soro de 250 indivíduos foram analisadas. RESULTADOS: Destas, 40 e 118 foram positivas nos testes coproscópico e sorológico, respectivamente. Na coproscopia, 32 (80%) indivíduos tiveram testes positivos na primeira lâmina, 6 (15%) na segunda e 2 (5%) apenas na terceira lâmina. O desempenho do teste de ELISA no diagnóstico utilizando-se o método KK como referência de diagnóstico, demonstrou valor preditivo negativo de 100% mas a especificidade e o valor preditivo positivo foram de 62,8% e 33,9%, respectivamente. CONCLUSÕES: Neste estudo, o aumento de uma para três lâminas analisadas por amostra pelo KK, mostrou ser um procedimento útil para o aumento da sensibilidade diagnóstica desta técnica.

A simple approach improving the performance of urine reagent strips for rapid diagnosis of urinary schistosomiasis in Nigerian schoolchildren

In Nigeria, schistosomiasis, caused predominantly by the species Schistosoma haematobium, is highly endemic in resource-poor communities. We performed a school-based survey in two rural communities in Osun State (Southwestern Nigeria) and assessed macrohaematuria, microhaematuria and proteinuria as indirect indicators for the presence of disease. Urine samples were inspected macroscopically for haematuria and screened for microhaematuria and proteinuria using urine reagent strips. The microscopic examination of schistosome eggs was used as the gold standard for diagnosis. In total, 447 schoolchildren were included in this study and had a 51 percent prevalence of urinary schistosomiasis. The sensitivity of microhaematuria (68 percent) and proteinuria (53 percent) for infection with S. haematobium was relatively low. In patients with a heavy infection (>500 eggs/10 mL), the sensitivity of microhaematuria was high (95 percent). When the presence of macrohaematuria and the concomitant presence of microhaematuria and proteinuria were combined, it revealed a sensitivity of 63 percent, a specificity of 93 percent and a positive predictive value of 91 percent. Macrohaematuria also showed high specificity (96 percent) and a positive predictive value of 92 percent, while sensitivity was < 50 percent. These data show that combining urine reagent strip tests (presence of proteinuria and microhaematuria) and information on macrohaematuria increased the accuracy of the rapid diagnosis of urinary schistosomiasis in an endemic rural West African setting. This simple approach can be used to increase the quality of monitoring of schistosomiasis in schoolchildren.