Evaluation of urine-circulating cathodic antigen (Urine-CCA) cassette test for the detection of Schistosoma mansoni infection in areas of moderate prevalence in Ethiopia

Current and upcoming point-of-care diagnostics for schistosomiasis

Point-of-care (POC) diagnostics are simple and effective portable tools that can be used for fast mapping of helminthic diseases and monitoring control programs. Most POC tests (POCTs) available for schistosomiasis diagnosis are lateral flow immunoassays (LFIAs). The emergence of simple and rapid DNA isolation methods, along with isothermal nucleic acid amplification strategies - for example, loop-mediated isothermal amplification (LAMP) and recombinase polymerase amplification (RPA) - and recent clustered regularly interspaced short palindromic repeats (CRISPR)-based diagnostic methods facilitate the development of molecular-based POC diagnostics for schistosomiasis. Furthermore, smartphone-based techniques increase real-time connectivity and readout accuracy of POCTs. This review discusses the recent advances in immunological-, molecular-based POCTs and mobile phone microscopes for the diagnosis/screening of schistosomiasis.

Reproducibility matters: intra- and inter-sample variation of the point-of-care circulating cathodic antigen test in two Schistosoma mansoni endemic areas in Uganda

Over 240 million people are infected with schistosomiasis. Detecting Schistosoma mansoni eggs in stool using Kato-Katz thick smears (Kato-Katzs) is highly specific but lacks sensitivity. The urine-based point-of-care circulating cathodic antigen test (POC-CCA) has higher sensitivity, but issues include specificity, discrepancy between batches and interpretation of trace results. A semi-quantitative G-score and latent class analyses making no assumptions about trace readings have helped address some of these issues. However, intra-sample and inter-sample variation remains unknown for POC-CCAs. We collected 3 days of stool and urine from 349 and 621 participants, from high- and moderate-endemicity areas, respectively. We performed duplicate Kato-Katzs and one POC-CCA per sample. In the high-endemicity community, we also performed three POC-CCA technical replicates on one urine sample per participant. Latent class analysis was performed to estimate the relative contribution of intra- (test technical reproducibility) and inter-sample (day-to-day) variation on sensitivity and specificity. Within-sample variation for Kato-Katzs was higher than between-sample, with the opposite true for POC-CCAs. A POC-CCA G3 threshold most accurately assesses individual infections. However, to reach the WHO target product profile of the required 95% specificity for prevalence and monitoring and evaluation, a threshold of G4 is needed, but at the cost of reducing sensitivity. This article is part of the theme issue 'Challenges and opportunities in the fight against neglected tropical diseases: a decade from the London Declaration on NTDs'.

Accuracy of Diagnostic Tests for Detecting Schistosoma mansoni and S. haematobium in Sub-Saharan Africa: A Systematic Review and Meta-Analysis

Introduction

Schistosomiasis is causing high morbidity and significant mortality in endemic areas. Kato-Katz stool examination and urine filtration techniques are the conventional methods for the detection of intestinal and urinary schistosomiasis. The most appropriate diagnostic tools for the detection of schistosomiasis especially in low-prevalence settings should be used. Therefore, this study is aimed at investigating the diagnostic accuracy of S. mansoni and S. haematobium diagnostic tools in sub-Saharan Africa.

Methods

Electronic databases such as PubMed, PubMed Central/Medline, HINARI, Scopus, EMBASE, Science Direct, Google Scholar, and Cochrane Library were reviewed. The pooled estimates and heterogeneity were determined using Midas in Stata 14.0. The diagnostic accuracy of index tests was compared using the hierarchical summary of the receiver operating characteristic (HSROC) curve in Stata 14.0.

Results

Twenty-four studies consisting of 12,370 individuals were tested to evaluate the accuracy of antigen, antibody, and molecular test methods for the detection of S. mansoni and S. haematobium. The pooled estimate of sensitivity and specificity of CCA was 88% (95% CI: 83-92) and 72 (95% CI: 62-80), respectively, when it is compared with parasitological stool examination for S. mansoni detection. On the other hand, ELISA showed a pooled estimate of sensitivity and specificity of 95% (95% CI: 93-96) and 35% (95% CI: 21-52), respectively, for the examination of S. mansoni using stool examination as a reference test. With regard to S. haematobium, the pooled estimate of sensitivity and specificity of polymerase chain reaction was 97% (95% CI: 78-100) and 94% (95% CI: 74-99), respectively. Moreover, the sensitivity and specificity of urine CCA vary between 41-80% and 55-91%, respectively, compared to urine microscopy.

Conclusion

The effort of schistosomiasis elimination requires accurate case identification especially in low-intensity infections. This study showed that CCA had the highest sensitivity and moderate specificity for the diagnosis of S. mansoni. Similarly, the sensitivity of ELISA was excellent, but its specificity was low. The diagnostic accuracy of PCR for the detection of S. haematobium was excellent compared to urine microscopic examination.

Diagnosis of Schistosomiasis without a Microscope: Evaluating Circulating Antigen (CCA, CAA) and DNA Detection Methods on Banked Samples of a Community-Based Survey from DR Congo

Detection of Schistosoma eggs in stool or urine is known for its low sensitivity in diagnosing light infections. Alternative diagnostics with better sensitivity while remaining highly specific, such as real-time PCR and circulating antigen detection, are progressively used as complementary diagnostic procedures but have not yet replaced microscopy. This study evaluates these alternative methods for the detection of Schistosoma infections in the absence of microscopy. Schistosomiasis presence was determined retrospectively in 314 banked stool and urine samples, available from a previous survey on the prevalence of taeniasis in a community in the Democratic Republic of the Congo, using real-time PCR, the point-of-care circulating cathodic antigen (POC-CCA) test, as well as the up-converting particle lateral flow circulating anodic antigen (UCP-LF CAA) test. Schistosoma DNA was present in urine (3%) and stool (28%) samples, while CCA (28%) and CAA (69%) were detected in urine. Further analysis of the generated data indicated stool-based PCR and the POC-CCA test to be suitable diagnostics for screening of S. mansoni infections, even in the absence of microscopy. A substantial proportion (60%) of the 215 CAA-positive cases showed low antigen concentrations, suggesting that even PCR and POC-CCA underestimated the “true” number of schistosome positives.

High prevalence of Schistosoma mansoni infection and stunting among school age children in communities along the Albert-Nile, Northern Uganda: A cross sectional study

BACKGROUND

Knowing the prevalence of schistosomiasis is key to informing programmes to control and eliminate the disease as a public health problem. It is also important to understand the impact of infection on child growth and development in order to allocate appropriate resources and effort to the control of the disease.

METHODS

We conducted a survey to estimate the prevalence of schistosomiasis among school aged children in villages along the Albert-Nile shore line in the district of Pakwach, North Western Uganda. A total of 914 children aged between 10-15 years were screened for Schistosoma mansoni using the POC-CCA and Kato Katz (KK) techniques. The infection intensities were assessed by POC-CCA and KK as well as CAA tests. The KK intensities were also correlated with POC-CCA and with CAA intensity. Anthropometric measurements were also taken and multivariate analysis was carried out to investigate their association with infection status.

RESULTS

The prevalence of schistosomiasis using the POC-CCA diagnostic test was estimated at 85% (95% CI: 83-87), being highest amongst children living closer to the Albert-Nile shoreline. Visual scoring of the POC-CCA results was more sensitive than the Kato Katz test and was positively correlated with the quantified infection intensities by the CAA test. The majority of the children were underweight (BMI<18.5), and most notably, boys had significantly lower height for age (stunting) than girls in the same age range (p < 0.0001), but this was not directly associated with S. mansoni infection.

CONCLUSION

High prevalence of S. mansoni infection in the region calls for more frequent mass drug administration with praziquantel. We observed high levels of stunting which was not associated with schistosomiasis. There is a need for improved nutrition among the children in the area.

Field assessment in Cameroon of a reader of POC-CCA lateral flow strips for the quantification of Schistosoma mansoni circulating cathodic antigen in urine

Background

Determining Schistosoma mansoni infection rate and intensity is challenging due to the low sensitivity of the Kato-Katz (KK) test that underestimates the true disease prevalence. Circulating cathodic antigen (CCA) excreted in urine is constantly produced by adult worms and has been used as the basis of a simple, non-invasive point of care test (POC-CCA) for Schistosoma mansoni infections. Although the abundance of CCA in urine is proportional to worm burden, the POC-CCA test is marketed as a qualitative test, making it difficult to investigate the wide range of infection intensities. This study was designed to compare the prevalence and intensity of S. mansoni by KK and POC-CCA and quantify, on fresh and frozen (<-20°C) urine samples, CCA using the visual scores and the ESEquant LR3 reader.

Methodology

Stool and urine samples were collected from 759 school-aged children. The prevalence and intensity of S. mansoni were determined using KK and POC-CCA. The degree of the positivity of POC-CCA was estimated by quantifying CCA on fresh and frozen urine samples using visual scores and strip reader. The prevalence, the infection intensity as well the relative amounts of CCA were compared.

Results

The S. mansoni infection rates inferred from POC-CCA and KK were 40.7% and 9.4% respectively. Good correlations were observed between infection intensities recorded by; i) the reader and visual scoring system on fresh (Rho = 0.89) and frozen samples (Rho = 0.97), ii) the reader on fresh urine samples and KK (epg) (Rho = 0.44). Nevertheless, 238 POC-CCA positive children were negative for KK, and sixteen of them had high levels of CCA. The correlation between results from the reader on fresh and frozen samples was good (Rho = 0.85). On frozen samples, CCA was not detected in 55 samples that were positive in fresh urine samples.

Conclusion

This study confirmed the low sensitivity of KK and the high capacity of POC-CCA to provide reliable data on the prevalence and intensity of S. mansoni infections. The lateral flow reader enabled accurate quantification of CCA under field conditions on fresh and frozen urine samples with less time and effort than KK.

Diagnosis of schistosomiasis has relied on the Kato-Katz technique which remains challenging due to its low sensitivity. To overcome this limitation, the Point-of-care-Circulating Cathodic Antigen (POC-CCA) test has been developed to detect CCA produced by adult living worm. However, this test is sold for qualitative use only because it is difficult to estimate the intensity of the positive band by eye. This study was designed with the aim of comparing the prevalence and intensity of S. mansoni infections by KK and POC-CCA and quantifying under field conditions on fresh and frozen (<-20°C) urine samples, CCA using the visual scores and the ESEquant LR3 reader. We conducted the KK and POC-CCA tests on stool and urine samples collected from SAC (5 to 4 years) in Makenene, Cameroon. Our results showed discrepancies between results from KK and POC-CCA test. The numerical values generated by the reader made it possible to avoid subjective visual interpretation of POC-CCA results. This study also identified children with high levels of CCA in their urine but without schistosome eggs in their stools. The good correlation observed between results obtained on fresh and frozen urine samples confirmed that POC-CCA test can be used on samples stored for one year at -20° C.

Biogeographical characteristics of Schistosoma mansoni endemic areas in Ethiopia: a systematic review and meta analysis

BACKGROUND

In Ethiopia, schistosomiasis is caused by Schistosoma mansoni and S. haematobium with the former being widespread and more than 4 million people are estimated to be infected by S. mansoni annually with 35 million at risk of infection. Although many school- and community-based epidemiological surveys were conducted over the past decades, the national distribution of schistosomiasis endemic areas and associated socio-environmental determinants remain less well understood. In this paper, we review S. mansoni prevalence of infections and describe key biogeographical characteristics in the endemic areas in Ethiopia.

METHODS

We developed a database of S. mansoni infection surveys in Ethiopia through a systematic review by searching articles published between 1975 and 2019 on electronic online databases including PubMed, ScienceDirect, and Web of Science. A total of 62 studies involving 95 survey locations were included in the analysis. We estimated adjusted prevalence of infection from each survey by considering sensitivity and specificity of diagnostic tests using Bayesian approach. All survey locations were georeferenced and associated environmental and geographical characteristics (e.g. elevation, normalized difference vegetation index, soil properties, wealth index, and climatic data) were described using descriptive statistics and meta-analysis.

RESULTS

The results showed that the surveys exhibited a wide range of adjusted prevalence of infections from 0.5% to 99.5%, and 36.8% of the survey sites had adjusted prevalence of infection higher than 50%. S. mansoni endemic areas were distributed in six regional states with the majority of surveys being in Amhara and Oromia. Endemic sites were found at altitudes from 847.6 to 3141.8 m above sea level, annual mean temperatures between 17.9 and 29.8 ℃, annual cumulative precipitation between 1400 and 1898 mm, normalized difference vegetation index between 0.03 and 0.8, wealth index score between -68 857 and 179 756; and sand, silt, and clay fraction in soil between 19.1-47.2, 23.0-36.7, and 20.0-52.8 g/100 g, respectively.

CONCLUSIONS

The distribution of S. mansoni endemic areas and prevalence of infections exhibit remarked environmental and ecological heterogeneities. Future research is needed to understand how much these heterogeneities drive the parasite distribution and transmission in the region.

Analysis of Daily Variation for 3 and for 30 Days of Parasite-Specific IgG in Urine for Diagnosis of Strongyloidiasis by Enzyme-Linked Immunosorbent Assay

Recent work has found urine analysis to be as sensitive as serology for diagnosis of strongyloidiasis. Here, we examined the daily variation of Strongyloides-specific IgG in urine by qualitative and quantitative ELISA and its effects on diagnostic accuracy and reliability. In the first part of the study, matched urine and fecal samples were collected from project participants in northeast Thailand for three consecutive days. Urine samples were analyzed for Strongyloides-specific IgG by ELISA using Strongyloides ratti as the antigen source. Performance of urine ELISA was compared with parasitological diagnosis by agar plate culture technique (APCT) and formalin-ethyl acetate concentration technique (FECT). In the second part of the study, urine IgG levels were compared daily for thirty consecutive days. The prevalence of Strongyloides infection, as measured by urine ELISA for three consecutive days, was significantly higher than that found using parasitological methods (63.1% vs. 22%). There was slight daily variation in prevalence estimates according to urine ELISA while there were significant variations according to parasitological examination methods over three consecutive days. For the 3-day experiment, urine ELISA had 83-86% diagnostic sensitivity when compared with the fecal examination method or with a composite standard (combined results from fecal examination methods (APCT or FECT) and/or urine ELISA). The levels of parasite-specific IgG in urine were stable throughout both the 3-day and the 30-day studies. In conclusion, diagnosis of strongyloidiasis by urine ELISA is more sensitive than by fecal methods, with minimal daily variation for qualitative and quantitative diagnosis. Urine ELISA has potential for clinical diagnosis and population screening of strongyloidiasis.

Estimating true prevalence of Schistosoma mansoni from population summary measures based on the Kato-Katz diagnostic technique

BACKGROUND

The prevalence of Schistosoma mansoni infection is usually assessed by the Kato-Katz diagnostic technique. However, Kato-Katz thick smears have low sensitivity, especially for light infections. Egg count models fitted on individual level data can adjust for the infection intensity-dependent sensitivity and estimate the 'true' prevalence in a population. However, application of these models is complex and there is a need for adjustments that can be done without modeling expertise. This study provides estimates of the 'true' S. mansoni prevalence from population summary measures of observed prevalence and infection intensity using extensive simulations parametrized with data from different settings in sub-Saharan Africa.

METHODOLOGY

An individual-level egg count model was applied to Kato-Katz data to determine the S. mansoni infection intensity-dependent sensitivity for various sampling schemes. Observations in populations with varying forces of transmission were simulated, using standard assumptions about the distribution of worms and their mating behavior. Summary measures such as the geometric mean infection, arithmetic mean infection, and the observed prevalence of the simulations were calculated, and parametric statistical models fitted to the summary measures for each sampling scheme. For validation, the simulation-based estimates are compared with an observational dataset not used to inform the simulation.

PRINCIPAL FINDINGS

Overall, the sensitivity of Kato-Katz in a population varies according to the mean infection intensity. Using a parametric model, which takes into account different sampling schemes varying from single Kato-Katz to triplicate slides over three days, both geometric and arithmetic mean infection intensities improve estimation of sensitivity. The relation between observed and 'true' prevalence is remarkably linear and triplicate slides per day on three consecutive days ensure close to perfect sensitivity.

CONCLUSIONS/SIGNIFICANCE

Estimation of 'true' S. mansoni prevalence is improved when taking into account geometric or arithmetic mean infection intensity in a population. We supply parametric functions and corresponding estimates of their parameters to calculate the 'true' prevalence for sampling schemes up to 3 days with triplicate Kato-Katz thick smears per day that allow estimation of the 'true' prevalence.

Evaluation, Validation, and Recognition of the Point-of-Care Circulating Cathodic Antigen, Urine-Based Assay for Mapping Schistosoma mansoni Infections

Efforts to control Schistosoma mansoni infection depend on the ability of programs to effectively detect and quantify infection levels and adjust programmatic approaches based on these levels and program goals. One of the three major objectives of the Schistosomiasis Consortium for Operational Research and Evaluation (SCORE) has been to develop and/or evaluate tools that would assist Neglected Tropical Disease program managers in accomplishing this fundamental task. The advent of a widely available point-of-care (POC) assay to detect schistosome circulating cathodic antigen (CCA) in urine with a rapid diagnostic test (the POC-CCA) in 2008 led SCORE and others to conduct multiple evaluations of this assay, comparing it with the Kato–Katz (KK) stool microscopy assay—the standard used for more than 45 years. This article describes multiple SCORE-funded studies comparing the POC-CCA and KK assays, the pros and cons of these assays, the use of the POC-CCA assay for mapping of S. mansoni infections in areas across the spectrum of prevalence levels, and the validation and recognition that the POC-CCA, although not infallible, is a highly useful tool to detect low-intensity infections in low-to-moderate prevalence areas. Such an assay is critical, as control programs succeed in driving down prevalence and intensity and seek to either maintain control or move to elimination of transmission of S. mansoni.

Contributions of the Schistosomiasis Consortium for Operational Research and Evaluation (SCORE) to Schistosomiasis Control and Elimination: Key Findings and Messages for Future Goals, Thresholds, and Operational Research

Herein, we summarize what we consider are major contributions resulting from the Schistosomiasis Consortium for Operational Research and Evaluation (SCORE) program, including its key findings and key messages from those findings. Briefly, SCORE's key findings are as follows: i) biennial mass drug administration (MDA) with praziquantel can control schistosomiasis to moderate levels of prevalence; ii) MDA alone will not achieve elimination; iii) to attain and sustain control throughout endemic areas, persistent hotspots need to be identified following a minimal number of years of annual MDA and controlled through adaptive strategies; iv) annual MDA is more effective than biennial MDA in high-prevalence areas; v) the current World Health Organization thresholds for decision-making based on the prevalence of heavy infections should be redefined; and vi) point-of-care circulating cathodic antigen urine assays are useful for Schistosoma mansoni mapping in low-to-moderate prevalence areas. The data and specimens collected and curated through SCORE efforts will continue to be critical resource for future research. Besides providing useful information for program managers and revision of guidelines for schistosomiasis control and elimination, SCORE research and outcomes have identified additional questions that need to be answered as the schistosomiasis community continues to implement effective, evidence-based programs. An overarching contribution of SCORE has been increased cohesiveness within the schistosomiasis field-oriented community, thereby fostering new and productive collaborations. Based on SCORE's findings and experiences, we propose new approaches, thresholds, targets, and goals for control and elimination of schistosomiasis, and recommend research and evaluation activities to achieve these targets and goals.

Evaluation of a rapid diagnostic test for Schistosoma mansoni infection based on the detection of circulating cathodic antigen in urine in Central Sudan

Background

The Kato-Katz thick smear is the standard test for the diagnosis of Schistosoma mansoni infection, but the sensitivity of this technique is low. As an alternative, (CCA) strip test has been evaluated with the conclusion that it may replace the Kato-Katz method in areas where prevalences are moderate or high. Therefore, this study was undertaken to evaluate the performance of the CCA strip test in the diagnosis and monitoring of S. mansoni infection in Sudan.

Methodology

489 stool and urine samples were collected from school children in endemic area of Sudan to determine the validity of CCA strip test based on duplicate Kato-Katz thick smear technique. Additional, 118 samples from known non schistosome-endemic area were collected to assess the CCA cross reactivity with other pathogens rather than schistosomiasis. The stability of CCA in urine samples was determined by consecutive examination of 40 positive CCA urine samples. 81 samples were used to evaluate the CCA strip test for the assessment of cure one week, three weeks and six weeks post Praziquantel treatment.

Principal findings

Assuming parasitological test results as the gold standard, the sensitivity, specificity, positive predictive and negative predictive values of the CCA test were 96%, 85.4%, 78.5% and 97.5% respectively. There was no cross reactivity with other pathogens. The CCA strip test showed high accuracy in monitoring of treatment 93.8% and 100% after three and six weeks of administration of Praziquantel respectively. The stability of the CCA for long time in the urine revealed a safety transportation and shipment of the samples whenever it demanded.

Conclusion/Significance

The uses of urine CCA strip test in the field would provide more accurate information on the epidemiology and monitoring of the Schistosoma mansoni infection in endemic areas of schistosomiasis than the conventional parasitological method. Moreover, The stability of CCA in urine samples confirms a safety transportation period of the samples whenever it required.

A newly developed one-step reagent strip test for detection of S. mansoni circulating cathodic antigen (CCA) in urine was evaluated in different countries and claimed that it has high sensitivity as well as specificity for the epidemiological study of schistosomiasis. However, it is of practical importance to evaluate the effectiveness of such a new technique in several schistosomiasis-endemic areas prior to its application for routine diagnosis or epidemiological study of the disease. Therefore, the present study aimed to evaluate this new method in order to be adopted and applied in the Sudan to improve the diagnosis and to assist in the control of schistosomiasis. 489 school children in central Sudan were examined for stool and urine using Kato-Katz technique and CCA strip test for S. mansoni infection. The sensitivity, specificity, positive predictive and negative predictive values of the CCA test were 96%, 85.4%, 78.5% and 97.5% respectively. The CCA strip test also showed high accuracy in monitoring of treatment 93.8% and 100% after three and six weeks of administration of Praziquantel respectively. Therefore, the uses of urine CCA strip test in the field would provide more accurate information on the epidemiology and monitoring of the Schistosoma mansoni infection in endemic areas of schistosomiasis. Additional assessment is recommended in areas with lower schistosomiasis prevalence and intensity levels.

The Advances in Molecular and New Point-of-Care (POC) Diagnosis of Schistosomiasis Pre- and Post-praziquantel Use: In the Pursuit of More Reliable Approaches for Low Endemic and Non-endemic Areas

Like soil-transmitted helminth infections, schistosomiasis is an important neglected tropical disease (NTD) related to poverty with a major impact on public health in developing countries. Diagnosis of active infection is crucial for surveillance of controlled or post-elimination schistosomiasis areas. In addition, the use of conventional diagnostic tools in non-exposed populations (such as travelers) results in misdiagnoses in the prepatent period of infection. Also, the accuracy of standard tests applied in low-endemicity areas (LEAs) decreases after several rounds of treatment. We aimed to determine whether it would be necessary to replace schistosomiasis conventional diagnostic tests such as parasitological methods in LEAs. Also, we evaluate the use of new tools in non-endemic areas. Reliable, cheap and easy-to-use diagnostic tools are needed to respond to the demands of a new era of elimination and eradication of schistosomiasis. To this end, molecular diagnosis-including nucleic acid-based assays (loop-mediated isothermal amplification, polymerase chain reaction) and circulating cathodic and anodic antigen detection tests have become promising strategies. In this review, we attempt to address the use of alternative diagnostic tests for active infection detection and drug-monitoring after specific schistosomiasis treatment.

Comparing the performance of urine and copro-antigen detection in evaluating Opisthorchis viverrini infection in communities with different transmission levels in Northeast Thailand

To combat and eventually eliminate the transmission of the liver fluke Opisthorchis viverrini, an accurate and practical diagnostic test is required. A recently established urine antigen detection test using monoclonal antibody-based enzyme-linked-immunosorbent assay (mAb-ELISA) has shown promise due to its high diagnostic accuracy and the use of urine in place of fecal samples. To further test the utility of this urine assay, we performed a cross sectional study of 1,043 people in 3 opisthorchiasis endemic communities in northeast Thailand by applying urine antigen detection together with copro-antigen detection methods. The quantitative formalin-ethyl acetate concentration technique (FECT) was concurrently performed as a reference method. The prevalence of O. viverrini determined by urine antigen detection correlated well with that by copro-antigen detection and both methods showed 10-15% higher prevalence than FECT. Within the fecal negative cases by FECT, 29% and 43% were positive by urine and copro-antigen detection, respectively. The prevalence and intensity profiles determined by antigen detection and FECT showed similar patterns of increasing trends of infection with age. The concentration of antigen measured in urine showed a positive relationship with the concentration of copro-antigen, both of which were positively correlated with fecal egg counts. The data observed in this study indicate that urine antigen detection had high diagnostic accuracy and was in concordance with copro-antigen detection. Due to the ease and noninvasiveness of sample collection, the urine assay has high potential for clinical diagnosis as well as population screening in the program for the control and elimination of opisthorchiasis.

Translating preventive chemotherapy prevalence thresholds for Schistosoma mansoni from the Kato-Katz technique into the point-of-care circulating cathodic antigen diagnostic test

BACKGROUND

Intervention guidelines against Schistosoma mansoni are based on the Kato-Katz technique. However, Kato-Katz thick smears show low sensitivity, especially for light-intensity infections. The point-of-care circulating cathodic antigen (POC-CCA) is a promising rapid diagnostic test detecting antigen output of living worms in urine and results are reported as trace, 1+, 2+, and 3+. The use of POC-CCA for schistosomiasis mapping, control, and surveillance requires translation of the Kato-Katz prevalence thresholds into POC-CCA relative treatment cut-offs. Furthermore, the infection status of egg-negative but antigen-positive individuals and the intensity-dependent sensitivity of POC-CCA should be estimated to determine its suitability for verification of disease elimination efforts.

METHODOLOGY

We used data from settings in Africa and the Americas characterized by a wide range of S. mansoni endemicity. We estimated infection intensity-dependent sensitivity and specificity of each test at the unit of the individual, using a hierarchical Bayesian egg-count model that removes the need to define a 'gold' standard applied to data with multiple Kato-Katz thick smears and POC-CCA urine cassette tests. A simulation study was carried out based on the model estimates to assess the relation of the two diagnostic tests for different endemicity scenarios.

PRINCIPAL FINDINGS

POC-CCA showed high specificity (> 95%), and high sensitivity (> 95%) for moderate and heavy infection intensities, and moderate sensitivity (> 75%) for light infection intensities, and even for egg-negative but antigen-positive infections. A 10% duplicate slide Kato-Katz thick smear prevalence corresponded to a 15-40% prevalence of ≥ trace-positive POC-CCA, and 10-20% prevalence of ≥ 1+ POC-CCA. The prevalence of ≥ 2+ POC-CCA corresponded directly to single slide Kato-Katz prevalence for all prevalence levels.

CONCLUSIONS/SIGNIFICANCE

The moderate sensitivity of POC-CCA, even for very light S. mansoni infections where the sensitivity of Kato-Katz is very low, and the identified relationship between Kato-Katz and POC-CCA prevalence thresholds render the latter diagnostic tool useful for surveillance and initial estimation of elimination of S. mansoni. For prevalence below 10% based on a duplicate slide Kato-Katz thick smear, we suggest using POC-CCA including trace results to evaluate treatment needs and propose new intervention thresholds that need to be validated in different settings.

Comparison of sensitivity and specificity of three diagnostic tests to detect Schistosoma mansoni infections in school children in Mwanza region, Tanzania

Background

Schistosomiasis remains one of the most prevalent parasitic infections in the world and has significant economic and public health consequences, particularly in poor communities. Reliable and accurate diagnosis plays a key role in surveillance, prevention and control of schistosomiasis. Currently, the microscopic Kato Katz (KK) stool thick smear technique is the most commonly used method to diagnose Schistosoma mansoni infections in epidemiological surveys. It is well-known that the sensitivity of this parasitological method decreases when infection intensities are moderate to low, however. The urine-based Point-of Care Circulating Cathodic Antigen (POC-CCA) test has been extensively evaluated as a further diagnostic tool. Several studies have shown that the POC-CCA test is more sensitive but less specific than the KK method. However, to clarify the meaning of inconsistent results between KK and POC-CCA tests in clinical routine, this study compares the accuracy of microscopy and POC-CCA versus real-time polymerase chain reaction (real-time PCR) results of urine and faecal samples from African school children participants.

Methodology

This was a school-based cross-sectional study conducted in 2015 among 305 school children aged 7–16 years from two primary schools located in Ilemela and Magu Districts, north-western Tanzania. Single stool and urine samples were collected from each participant and examined for the presence of Schistosoma mansoni eggs, parasite antigen, and parasite DNA using KK thick smears, POC-CCA tests, and real-time PCR, respectively.

Principal findings

The prevalence of S. mansoni infection, calculated by KK was 85.2%, by real-time PCR 92.9% and by POC-CCA 94.9%. In comparison to KK, the POC-CCA and real-time PCR tests had sensitivities of 89.7% and 99.5% and specificities of 22.73% and 29.55%, respectively. However, due to the known limitations of the KK assay, we also used latent class analysis (LCA) that included POC-CCA, KK, and schistosome-specific real-time PCR results to determine their sensitivities and specificities. The POC-CCA test had the highest sensitivity (99.5%) and a specificity of 63.4% by LCA and the real-time PCR test had a sensitivity of 98.7% and the highest specificity (81.2%).

Conclusion

In moderate and high prevalence areas, the POC-CCA cassette test is more sensitive than the KK method and can be used for screening and geographical mapping of S. mansoni infections. Real-time PCR is highly sensitive and also shows the highest specificity among the 3 investigated diagnostic procedures. It can offer added value in diagnosing schistosomiasis.

Comparing the performance of circulating cathodic antigen and Kato-Katz techniques in evaluating Schistosoma mansoni infection in areas with low prevalence in selected counties of Kenya: a cross-sectional study

BACKGROUND

Kato-Katz technique has been the mainstay test in Schistosoma mansoni diagnosis in endemic areas. However, recent studies have documented its poor sensitivity in evaluating Schistosoma mansoni infection especially in areas with lower rates of transmission. It's the primary diagnostic tool in monitoring impact of the Kenya national school based deworming program on infection transmission, but there is need to consider a more sensitive technique as the prevalence reduces. Therefore, this study explored the relationship between results of the stool-based Kato-Katz technique with urine-based point-of-care circulating cathodic antigen (POC-CCA) test in view to inform decision-making by the program in changing from Kato-Katz to POC-CCA test.

METHODS

We used two cross-sectional surveys conducted pre- and post- mass drug administration (MDA) using praziquantel in a representative random sample of children from 18 schools across 11 counties. A total of 1944 children were randomly sampled for the study. Stool and urine samples were tested for S. mansoni infection using Kato-Katz and POC-CCA methods, respectively. S. mansoni prevalence using each technique was calculated and 95% confidence intervals obtained using binomial regression model. Specificity (Sp) and sensitivity (Sn) were determined using 2 × 2 contingency tables and compared using the McNemar's chi-square test.

RESULTS

A total of 1899 and 1878 children were surveyed at pre- and post-treatment respectively. S. mansoni infection prevalence was 26.5 and 21.4% during pre- and post-treatment respectively using POC-CCA test, and 4.9 and 1.5% for pre- and post-treatment respectively using Kato-Katz technique. Taking POC-CCA as the gold standard, Kato-Katz was found to have significantly lower sensitivity both at pre- and post-treatment, Sn = 12.5% and Sn = 5.2% respectively, McNemar test χ²_m = 782.0, p < 0.001. In overall, the results showed a slight/poor agreement between the two methods, kappa index (k) = 0.11, p < 0.001, inter-rater agreement = 77.1%.

CONCLUSIONS

Results showed POC-CCA technique as an effective, sensitive and accurate screening tool for Schistosoma mansoni infection in areas of low prevalence. It was up to 14-fold accurate than Kato-Katz which had extremely inadequate sensitivity. We recommend usage of POC-CCA alongside Kato-Katz examinations by Schistosomiasis control programs in low prevalence areas.

Interpreting ambiguous 'trace' results in Schistosoma mansoni CCA Tests: Estimating sensitivity and specificity of ambiguous results with no gold standard

BACKGROUND

The development of new diagnostics is an important tool in the fight against disease. Latent Class Analysis (LCA) is used to estimate the sensitivity and specificity of tests in the absence of a gold standard. The main field diagnostic for Schistosoma mansoni infection, Kato-Katz (KK), is not very sensitive at low infection intensities. A point-of-care circulating cathodic antigen (CCA) test has been shown to be more sensitive than KK. However, CCA can return an ambiguous 'trace' result between 'positive' and 'negative', and much debate has focused on interpretation of traces results.

METHODOLOGY/PRINCIPLE FINDINGS

We show how LCA can be extended to include ambiguous trace results and analyse S. mansoni studies from both Côte d'Ivoire (CdI) and Uganda. We compare the diagnostic performance of KK and CCA and the observed results by each test to the estimated infection prevalence in the population. Prevalence by KK was higher in CdI (13.4%) than in Uganda (6.1%), but prevalence by CCA was similar between countries, both when trace was assumed to be negative (CCAtn: 11.7% in CdI and 9.7% in Uganda) and positive (CCAtp: 20.1% in CdI and 22.5% in Uganda). The estimated sensitivity of CCA was more consistent between countries than the estimated sensitivity of KK, and estimated infection prevalence did not significantly differ between CdI (20.5%) and Uganda (19.1%). The prevalence by CCA with trace as positive did not differ significantly from estimates of infection prevalence in either country, whereas both KK and CCA with trace as negative significantly underestimated infection prevalence in both countries.

CONCLUSIONS

Incorporation of ambiguous results into an LCA enables the effect of different treatment thresholds to be directly assessed and is applicable in many fields. Our results showed that CCA with trace as positive most accurately estimated infection prevalence.

The use of circulating cathodic antigen rapid test and serology for diagnosis of active Schistosoma mansoni infection in migrants in Italy, a non-endemic country: a cross sectional study

Diagnosis of schistosomiasis in migrants coming from endemic areas can be difficult, especially in asymptomatic subjects. Light-intensity disease, in fact, may be missed due to the low sensitivity of the stool microscopy and serologic testing cannot distinguish between a resolved infection and an active infection in patients who have been infected and treated in the past, because specific antibodies can persist despite cure. We describe a cross-sectional study conducted on 82 migrants tested for Schistosoma mansoni on single blood (anti-schistosome antibodies, total IgE) and urine [point-of-care (POC) circulating-cathodic-antigen (CCA) test] samples. A positive POC-CCA test (active infection) resulted in two untreated patients with a positive serology while all patients (n = 66) with a past infection showed a negative POC-CCA test. POC-CCA urine test in combination with serology may be helpful in rapidly differentiate active from past S. mansoni infection in migrants coming from endemic areas.

Field evaluation of a schistosome circulating cathodic antigen rapid test kit at point-of-care for mapping of schistosomiasis endemic districts in The Gambia

BACKGROUND

Studies in Sub Saharan Africa have shown that the Circulating Cathodic Antigen point-of-care-test (POC-CCA) is more accurate in the detections of S. mansoni than the microscopic Kato-Katz technique but less is known about the accuracy of this rapid test in detecting S. haematobium infections. This study was intended to evaluate the field accuracy of POC-CCA as a rapid test kit for schistosomiasis mapping in The Gambia.

METHODS

This prospective study was conducted in 4 regions in the country. Ten schools were randomly selected from each region, and a total of 2018 participants whose ages range from 7 to 14 years were enrolled in the study. Stool and urine samples were collected from each participant from May to June 2015, and tested for S. haematobium and S. mansoni infections in field and laboratory settings. The tests conducted included POC-CCA, double Kato-Katz slides, urine filtration and dipstick for hematuria.

RESULTS

Of the 1954 participants that had complete data, the mean age of participants was 9.9 years. The prevalence of children infected with S. haematobium, using urine filtration technique was 10.1% (95% CI: 8.87-11.55). Central River Region had the highest level of urinary schistosomiasis with a prevalence of 28.0% (24.13-32.12).The lowest urinary schistosomiasis prevalence of 0.6% (0.12-1.86) was found in Lower River Region and North Bank Region had no cases of schistosomiasis detected. Only 5 participants were infected with S. mansoni. Using urine filtration as reference standard for the detection of S. haematobium, the sensitivity and specificity of POC-CCA was 47.7% and 75.8%. Whilst sensitivity and specificity of POC-CCA for detecting S. mansoni were 60.0% and 71.2% using double Kato-Katz as reference standard.

CONCLUSION

This study showed lower sensitivity of POC-CCA in detecting S. haematobium. Therefore POC-CCA is less useful for rapid diagnosis of urinary schistosomiasis.

Serological approaches for the diagnosis of schistosomiasis - A review

Schistosomiasis is a common disease in endemic areas of Sub-Saharan Africa, South America and Asia. It is rare in Europe, mainly imported from endemic countries due to travelling or human migration. Available methods for the diagnosis of schistosomiasis comprise microscopic, molecular and serological approaches, with the latter detecting antigens or antibodies associated with Schistosoma spp. infection. The serological approach is a valuable screening tool in low-endemicity settings and for travel medicine, though the interpretation of any diagnostic results requires knowledge of test characteristics and a patient's history. Specific antibody detection by most currently used assays is only possible in a relatively late stage of infection and does not allow for the differentiation of acute from previous infections for therapeutic control or the discrimination between persisting infection and re-infection. Throughout the last decades, new target antigens have been identified, and assays with improved performance and suitability for use in the field have been developed. For numerous assays, large-scale studies are still required to reliably characterise assay characteristics alone and in association with other available methods for the diagnosis of schistosomiasis. Apart from S. mansoni, S. haematobium and S. japonicum, for which most available tests were developed, other species of Schistosoma that occur less frequently need to be taken into account. This narrative review describes and critically discusses the results of published studies on the evaluation of serological assays that detect antibodies against different Schistosoma species of humans. It provides insights into the diagnostic performance and an overview of available assays and their suitability for large-scale use or individual diagnosis, and thus sets the scene for serological diagnosis of schistosomiasis and the interpretation of results.

Evaluation and optimization of the Circulating Cathodic Antigen (POC-CCA) cassette test for detecting Schistosoma mansoni infection by using image analysis in school children in Mwanza Region, Tanzania

There is a need for diagnostic techniques which are sensitive, specific, rapid and easy to perform at the point-of-care. The aim of this study was to evaluate the diagnostic performance of the Circulating Cathodic Antigen (POC-CCA) assay for Schistosoma mansoni in four schools along the coast of Lake Victoria in Mwanza Region, Tanzania, and to optimize the reading of the POC-CCA test lines by using a computer software image analysis. Initially, a pilot study in 106 school children indicated that time of urine collection did not have an impact on CCA results as 84.9% (90) had identical scores from a urine collected in the morning and a urine taken at midday after drinking 0.5 L of water. The main study was conducted among 404 school children (aged 9–12 years) where stool and urine samples were collected for three consecutive days. For S. mansoni diagnosis, stool samples were examined for eggs with duplicate Kato-Katz smears, whereas urine samples were tested for presence of antigen by POC-CCA. The proportion of positive individuals for S. mansoni by one POC-CCA was higher compared to two Kato-Katz smears (66.1% vs. 28.7%; p < 0.0001). Both proportions increased expectedly when three POC-CCAs were compared to six Kato-Katz smears (75.0% vs. 42.6%; p < 0.0001). Three POC-CCAs were more sensitive (94.7%) than six Kato-Katz smears (53.8%) using the combined results of three POC-CCAs and six Kato-Katz smears as the ‘gold standard’. To optimize the reading of the POC-CCA, a Software tool (Image Studio Lite®) was used to read and quantify the colour (expressed as pixels) of the test line on all positive tests, showing a positive correlation between number of pixels and the visually scored intensities and between number of pixels and egg counts. In conclusion, the POC-CCA assay seems to be a more appropriate tool for S. mansoni diagnosis compared to the Kato-Katz method in endemic communities such as Mwanza Region. Optimization of the tool in terms of cassette-reading could be assessed by computer software which was able to quantify the colour of the lines in the strip of the cassette.

Accuracy of point-of-care testing for circulatory cathodic antigen in the detection of schistosome infection: systematic review and meta-analysis

OBJECTIVE

To assess the accuracy of point-of-care testing for circulatory cathodic antigen in the diagnosis of schistosome infection.

METHODS

We searched MEDLINE, EMBASE, LILACS and other bibliographic databases for studies published until 30 September 2015 that described circulatory cathodic antigen testing compared against one to three Kato-Katz tests per subject - for Schistosoma mansoni - or the filtration of one 10-ml urine sample per subject - for S. haematobium. We extracted the numbers of true positives, false positives, true negatives and false negatives for the antigen testing and performed meta-analyses using a bivariate hierarchical regression model.

FINDINGS

Twenty-six studies published between 1994 and 2014 met the inclusion criteria. In the detection of S. mansoni, a single antigen test gave a pooled sensitivity of 0.90 (95% confidence interval, CI: 0.84-0.94) and a pooled specificity of 0.56 (95% CI: 0.39-0.71; n = 7) when compared against a single Kato-Katz test. The corresponding values from comparisons with two to three Kato-Katz tests per subject were 0.85 (95% CI: 0.80-0.88) and 0.66 (95% CI: 0.53-0.76; n = 14), respectively. There appeared to be no advantage in using three antigen tests per subject instead of one. When compared against the results of urine filtration, antigen testing for S. haematobium showed poor sensitivity and poor specificity. The performance of antigen testing was better in areas of high endemicity than in settings with low endemicity.

CONCLUSION

Antigen testing may represent an effective tool for monitoring programmes for the control of S. mansoni.

Comparison of Schistosoma mansoni Prevalence and Intensity of Infection, as Determined by the Circulating Cathodic Antigen Urine Assay or by the Kato-Katz Fecal Assay: A Systematic Review

The relationship between results from Kato-Katz (KK) fecal microscopy and urine-based point-of-care circulating cathodic antigen (POC-CCA) assays for Schistosoma mansoni infection remains a critical issue. This systematic literature review of 25 published papers compares prevalence of S. mansoni infection by KK with that by the POC-CCA assay. Nineteen published studies met our inclusion criteria for data extraction and analysis. Above a prevalence of 50% by KK, KK and POC-CCA results yielded essentially the same prevalence. Below 50% prevalence by KK, the prevalence by the POC-CCA assay was between 1.5- and 6-fold higher and increased as prevalence by KK decreased. Five of nine publications met inclusion criteria for extractable data on intensity of S. mansoni infection by KK assay and visual band density using the POC-CCA assay. A clear positive relationship exists between intensity by the KK and POC-CCA assays. This systematic review indicates that below 50% prevalence, the POC-CCA assay is much more sensitive than the KK assay. 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.

Evaluation of the CCA Immuno-Chromatographic Test to Diagnose Schistosoma mansoni in Minas Gerais State, Brazil

Background

The Kato-Katz (KK) stool smear is the standard test for the diagnosis of Schistosoma mansoni infection, but suffers from low sensitivity when infections intensities are moderate to low. Thus, misdiagnosed individuals remain untreated and contribute to the disease transmission, thereby forestalling public health efforts to move from a modality of disease control to one of elimination. As an alternative, the urine-based diagnosis of schistosomiasis mansoni via the circulating cathodic antigen immuno-chromatographic test (CCA-ICT) has been extensively evaluated in Africa with the conclusion that it may replace the KK test in areas where prevalences are moderate or high.

Methods and Findings

The objective was to measure the performance of the CCA-ICT in a sample study population composed of residents from non-endemic and endemic areas for schistosomiasis mansoni in two municipalities of Minas Gerais state, Brazil. Volunteers (130) were classified into three infection status groups based on duplicate Kato-Katz thick smears from one stool sample (2KK test): 41 negative individuals from non-endemic areas, 41 negative individuals from endemic areas and 48 infected individuals from endemic areas. Infection status was also determined by the CCA-ICT and infection exposure by antibody ELISA (enzyme-linked immunosorbent assay) to S. mansoni soluble egg antigen (SEA) and soluble (adult) worm antigen preparation (SWAP). Sensitivity and specificity were influenced by whether the trace score visually adjudicated in the CCA-ICT was characterized as positive or negative for S. mansoni infection. An analysis of a two-graph receiver operating characteristic was performed to change the cutoff point. When the trace score was interpreted as a positive rather than as a negative result, the specificity decreased from 97.6% to 78.0% whereas sensitivity increased from 68.7% to 85.4%. A significantly positive correlation between the CCA-ICT scores and egg counts was identified (r = 0.6252, p = 0.0001). However, the CCA-ICT misdiagnosed as negative 14.6% of 2KK positive individuals, predominantly those with light infections (fewer than 100 eggs/g feces). Considering 2KK as reference test, the discriminating power of the CCA-ICT (the area under the curve [AUC] = 0.817) was greater than the SEA-ELISA (AUC = 0.744) and SWAP-ELISA (AUC = 0.704).

Conclusion

Our data for the performance of the CCA-ICT in the Brazilian communities endemic for schistosomiasis mansoni support those from Africa, i.e., in areas with greater infection prevalence and intensities, the CCA-ICT may be useful as a tool to indicate community-based preventative chemotherapy without individual diagnosis. However, because of the Brazilian Ministry of Health’s recommendation for individual diagnosis in areas where prevalence is less than 15%, i.e., those areas in which infection intensities are likely to be lowest, the CCA-ICT lacks the sensitivity to be used as standalone diagnostic tool.

Detecting parasite eggs in stool by the Kato-Katz (KK) stool smear is the standard diagnostic test for infection with the flatworm parasite, Schistosoma mansoni. However, the test can miss those who have low burdens of infection, i.e., with few eggs in their feces. These misdiagnosed individuals, therefore, do not receive drug treatment and can continue to transmit the parasite into the environment putting the community at risk of infection. As an alternative diagnostic approach, the circulating cathodic antigen immuno-chromatographic test (CCA-ICT) is a simple-to-use handheld device (similar to a pregnancy test) that only needs urine to provide a quick and visual indication of whether one is infected or not. The consensus from studies in Africa is that the CCA-ICT could replace the KK test in those areas where people are more likely to harbor moderate to high worm burdens (i.e., more eggs in stool), but, like the KK test, it can miss those harboring light infection intensities. We evaluated the CCA-ICT performance in urine samples from 130 individuals living in areas non-endemic and endemic for schistosomiasis mansoni within the municipalities of Governador Valadares and Manhuaçu, Minas Gerais state, Brazil. The CCA-ICT performance characteristics, chiefly, sensitivity and specificity, depended on whether a ‘trace’ visual reading of the test was considered as a positive or negative diagnosis. We noted a positive correlation between the CCA-ICT scores and egg counts. However, the CCA-ICT misdiagnosed as negative about 15% of KK positive individuals, predominantly those with light infections. The CCA-ICT, nonetheless, had better discriminating power than commonly used antibody-based tests. We conclude that the CCA-ICT offers reasonable performance to diagnosis S. mansoni infection. However, in areas where infections intensities are light, the test lacks the sensitivity to be used as standalone diagnostic tool.

Early lessons from schistosomiasis mass drug administration programs

Mass drug administration using praziquantel is the backbone of the current strategy for the control of schistosomiasis. As the theoretical plans have moved into practical application, certain challenges with this approach have surfaced, and it is likely that annual mass drug administration alone may not be sufficient to achieve program goals. However, mass drug administration is still the only available intervention that can be readily used in the wide variety of settings where schistosomiasis is endemic. The task then becomes how to improve this approach and identify what adjuncts to mass drug administration are effective, as programs move from morbidity control to elimination goals. Other aspects worthy of consideration include how best to employ new diagnostic tools to more easily identify where treatment is needed, and new formulations of praziquantel to extend the availability of treatment to all age groups. The aim of this review is to highlight both areas of challenge and of opportunity to improve the public health impact of schistosomiasis control programs.

Use of Occult Blood Detection Cards for Real-Time PCR-Based Diagnosis of Schistosoma Mansoni Infection

Background

In Schistosoma mansoni infection, diagnosis and control after treatment mainly rely on parasitological stool investigations which are laborious and have limited sensitivity. PCR methods have shown equal or superior sensitivity but preservation and storage methods limit their use in the field. Therefore, the use of occult blood detection cards (fecal cards) for easy sampling and storage of fecal samples for further PCR testing was evaluated in a pilot study.

Methodology

Stool specimens were collected in a highly endemic area for S. mansoni in Ethiopia and submitted in an investigator-blinded fashion to microscopic examination by Kato-Katz thick smear as well as to real-time PCR using either fresh frozen stool samples or stool smears on fecal cards which have been stored at ambient temperature for up to ten months.

Principal Findings

Out of 55 stool samples, 35 were positive by microscopy, 33 and 32 were positive by PCR of frozen samples and of fecal card samples, respectively. When microscopy was used as diagnostic “gold standard”, the sensitivity of PCR on fresh stool was 94.3% (95%-CI: 86.6; 100) and on fecal cards 91.4% (95%-CI: 82.2; 100).

Conclusions

The use of fecal cards proved to be a simple and useful method for stool collection and prolonged storage prior to PCR based diagnosis of S. mansoni infection. This technique may be a valuable approach for large scale surveillance and post treatment assessments

Diagnosis of neglected tropical diseases among patients with persistent digestive disorders (diarrhoea and/or abdominal pain ≥14 days): Pierrea multi-country, prospective, non-experimental case-control study

Background

Diarrhoea still accounts for considerable mortality and morbidity worldwide. The highest burden is concentrated in tropical areas where populations lack access to clean water, adequate sanitation and hygiene. In contrast to acute diarrhoea (<14 days), the spectrum of pathogens that may give rise to persistent diarrhoea (≥14 days) and persistent abdominal pain is poorly understood. It is conceivable that pathogens causing neglected tropical diseases play a major role, but few studies investigated this issue. Clinical management and diagnostic work-up of persistent digestive disorders in the tropics therefore remain inadequate. Hence, important aspects regarding the pathogenesis, epidemiology, clinical symptomatology and treatment options for patients presenting with persistent diarrhoea and persistent abdominal pain should be investigated in multi-centric clinical studies.

Methods/Design

This multi-country, prospective, non-experimental case–control study will assess persistent diarrhoea (≥14 days; in individuals aged ≥1 year) and persistent abdominal pain (≥14 days; in children/adolescents aged 1–18 years) in up to 2000 symptomatic patients and 2000 matched controls. Subjects from Côte d’Ivoire, Indonesia, Mali and Nepal will be clinically examined and interviewed using a detailed case report form. Additionally, each participant will provide a stool sample that will be examined using a suite of diagnostic methods (i.e., microscopic techniques, rapid diagnostic tests, stool culture and polymerase chain reaction) for the presence of bacterial and parasitic pathogens. Treatment will be offered to all infected participants and the clinical treatment response will be recorded. Data obtained will be utilised to develop patient-centred clinical algorithms that will be validated in primary health care centres in the four study countries in subsequent studies.

Discussion

Our research will deepen the understanding of the importance of persistent diarrhoea and related digestive disorders in the tropics. A diversity of intestinal pathogens will be assessed for potential associations with persistent diarrhoea and persistent abdominal pain. Different diagnostic methods will be compared, clinical symptoms investigated and diagnosis-treatment algorithms developed for validation in selected primary health care centres. The findings from this study will improve differential diagnosis and evidence-based clinical management of digestive syndromes in the tropics.

Trial registration

ClinicalTrials.gov; identifier: NCT02105714.

Application in Europe of a urine-based rapid diagnostic test for confirmation of Schistosoma mansoni infection in migrants from endemic areas

In February 2015, a male patient from Eritrea with persistent abdominal pain and rectal bleeding was diagnosed with Schistosoma mansoni infection upon examination of a rectal biopsy. In May 2015, repeated stool microscopy identified S. mansoni infection in another Eritrean patient with abdominal pain and considerable eosinophilia (34%). Use of point-of-care circulating cathodic antigen (POC-CCA) tests on urine confirmed S. mansoni infection in both patients. Wider application of non-invasive POC-CCA urine tests will improve schistosomiasis diagnosis and clinical management in migrants.

Evaluation of point-of-contact circulating cathodic antigen assays for the detection of Schistosoma mansoni infection in low-, moderate-, and high-prevalence schools in western Kenya

We evaluated the performance of a point-of-contact circulating cathodic antigen assay (POC-CCA) to detect schistosome infections in primary school children (N = 1,801) living in areas with low, moderate, and high Schistosoma mansoni prevalence in western Kenya. The commercially available assay (CCA-1) and a second, experimental formulation (CCA-2) were compared against Kato-Katz stool examinations and an anti-schistosome enzyme-linked immunosorbent assay (ELISA). A latent class model based on the four tests was used to establish "true infection status" in three different zones based on their distance from Lake Victoria. As a screening tool for community treatment according to World Health Organization (WHO) guidelines, the Kato-Katz examination was in closest agreement with the latent class model, followed by the experimental CCA-2, soluble adult worm antigen preparation (SWAP) ELISA, and CCA-1, which had high sensitivity compared with the other tests but was consistently the least specific. Our experience suggests that POC-CCA tests offer a field-friendly alternative to Kato-Katz, but need further interpretation for appropriate field use.

Circulating antigen tests and urine reagent strips for diagnosis of active schistosomiasis in endemic areas

BACKGROUND

Point-of-care (POC) tests for diagnosing schistosomiasis include tests based on circulating antigen detection and urine reagent strip tests. If they had sufficient diagnostic accuracy they could replace conventional microscopy as they provide a quicker answer and are easier to use.

OBJECTIVES

To summarise the diagnostic accuracy of: a) urine reagent strip tests in detecting active Schistosoma haematobium infection, with microscopy as the reference standard; and b) circulating antigen tests for detecting active Schistosoma infection in geographical regions endemic for Schistosoma mansoni or S. haematobium or both, with microscopy as the reference standard.

SEARCH METHODS

We searched the electronic databases MEDLINE, EMBASE, BIOSIS, MEDION, and Health Technology Assessment (HTA) without language restriction up to 30 June 2014.

SELECTION CRITERIA

We included studies that used microscopy as the reference standard: for S. haematobium, microscopy of urine prepared by filtration, centrifugation, or sedimentation methods; and for S. mansoni, microscopy of stool by Kato-Katz thick smear. We included studies on participants residing in endemic areas only.

DATA COLLECTION AND ANALYSIS

Two review authors independently extracted data, assessed quality of the data using QUADAS-2, and performed meta-analysis where appropriate. Using the variability of test thresholds, we used the hierarchical summary receiver operating characteristic (HSROC) model for all eligible tests (except the circulating cathodic antigen (CCA) POC for S. mansoni, where the bivariate random-effects model was more appropriate). We investigated heterogeneity, and carried out indirect comparisons where data were sufficient. Results for sensitivity and specificity are presented as percentages with 95% confidence intervals (CI).

MAIN RESULTS

We included 90 studies; 88 from field settings in Africa. The median S. haematobium infection prevalence was 41% (range 1% to 89%) and 36% for S. mansoni (range 8% to 95%). Study design and conduct were poorly reported against current standards. Tests for S. haematobium Urine reagent test strips versus microscopyCompared to microscopy, the detection of microhaematuria on test strips had the highest sensitivity and specificity (sensitivity 75%, 95% CI 71% to 79%; specificity 87%, 95% CI 84% to 90%; 74 studies, 102,447 participants). For proteinuria, sensitivity was 61% and specificity was 82% (82,113 participants); and for leukocyturia, sensitivity was 58% and specificity 61% (1532 participants). However, the difference in overall test accuracy between the urine reagent strips for microhaematuria and proteinuria was not found to be different when we compared separate populations (P = 0.25), or when direct comparisons within the same individuals were performed (paired studies; P = 0.21).When tests were evaluated against the higher quality reference standard (when multiple samples were analysed), sensitivity was marginally lower for microhaematuria (71% vs 75%) and for proteinuria (49% vs 61%). The specificity of these tests was comparable. Antigen assayCompared to microscopy, the CCA test showed considerable heterogeneity; meta-analytic sensitivity estimate was 39%, 95% CI 6% to 73%; specificity 78%, 95% CI 55% to 100% (four studies, 901 participants). Tests for S. mansoni Compared to microscopy, the CCA test meta-analytic estimates for detecting S. mansoni at a single threshold of trace positive were: sensitivity 89% (95% CI 86% to 92%); and specificity 55% (95% CI 46% to 65%; 15 studies, 6091 participants) Against a higher quality reference standard, the sensitivity results were comparable (89% vs 88%) but specificity was higher (66% vs 55%). For the CAA test, sensitivity ranged from 47% to 94%, and specificity from 8% to 100% (4 studies, 1583 participants).

AUTHORS' CONCLUSIONS

Among the evaluated tests for S. haematobium infection, microhaematuria correctly detected the largest proportions of infections and non-infections identified by microscopy.The CCA POC test for S. mansoni detects a very large proportion of infections identified by microscopy, but it misclassifies a large proportion of microscopy negatives as positives in endemic areas with a moderate to high prevalence of infection, possibly because the test is potentially more sensitive than microscopy.

Age-related factors influencing the occurrence of undernutrition in northeastern Ethiopia

Background

Undernutrition is a major public health problem on the globe particularly in the developing regions. The objective of the current study was to assess the prevalence of undernutrition in different age groups and examine the relationship of the disease to parasitic and socioeconomic factors among communities in Harbu Town, northeastern Ethiopia.

Methods

Stool samples of the study participants were examined for intestinal helminth infections using the Kato-Katz method. Blood specimens were diagnosed for Plasmodium infection using CareStartTM Malaria Pf/Pv Combo test. The blood type was determined from blood samples using antisera A and antisera B. In addition, the height and weight of the study participants was measured and information about their socioeconomic and sociodemographic characteristics was collected.

Results

Out of 484 individuals examined, 31.8% were undernourished and 32.0% were infected with intestinal helminths. The odds of undernutrition significantly decreased with an increase in the age of individuals. The prevalence of undernutrition in adults was significantly higher in males than in females and in those who had latrines than in those who did not have the facility. The odds of undernutrition in the 5 to 19 years age group was significantly higher in those who did not wash their hands before eating than in those who did. The prevalence of undernutrition in children younger than five years was significantly lower in those whose families were educated and had less than 5 family size compared to those with illiterate families and family size of greater than 5, respectively. However, the prevalence of undernutrition was similar in individuals who were infected and not infected with intestinal helminths. The intensity of Schistosoma mansoni infection was significantly higher among individuals of blood type A compared to those of type O.

Conclusions

Prevalence of undernutrition was higher in children than in adults and the association of sex and socioeconomic factors with undernutrition showed variation with age. However, helminth infection was not related with undernutrition in all age groups.

Tools for diagnosis, monitoring and screening of Schistosoma infections utilizing lateral-flow based assays and upconverting phosphor labels

The potential of various quantitative lateral flow (LF) based assays utilizing up-converting phosphor (UCP) reporters for the diagnosis of schistosomiasis is reviewed including recent developments. Active infections are demonstrated by screening for the presence of regurgitated worm antigens (genus specific polysaccharides), whereas anti-Schistosoma antibodies may indicate ongoing as well as past infections. The circulating anodic antigen (CAA) in serum or urine (and potentially also saliva) is identified as the marker that may allow detection of single-worm infections. Quantitation of antigen levels is a reliable method to study effects of drug administration, worm burden and anti-fecundity mechanisms. Moreover, the ratio of CAA and circulating cathodic antigen (CCA) is postulated to facilitate identification of either Schistosoma mansoni or Schistosoma haematobium infections. The UCP-LF assays allow simultaneous detection of multiple targets on a single strip, a valuable feature for antibody detection assays. Although antibody detection in endemic regions is not a useful tool to diagnose active infections, it gains potential when the ratio of different classes of antibody specific for the parasite/disease can be determined. The UCP-LF antibody assay format allows this type of multiplexing, including testing a linear array of up to 20 different targets. Multiple test spots would allow detection of specific antibodies, e.g. against different Schistosoma species or other pathogens as soil-transmitted helminths. Concluding, the different UCP-LF based assays for diagnosis of schistosomiasis provide a collection of tests with relatively low complexity and high sensitivity, covering the full range of diagnostics needed in control programmes for mapping, screening and monitoring.

Sensitivity and specificity of multiple Kato-Katz thick smears and a circulating cathodic antigen test for Schistosoma mansoni diagnosis pre- and post-repeated-praziquantel treatment

Background

Two Kato-Katz thick smears (Kato-Katzs) from a single stool are currently recommended for diagnosing Schistosoma mansoni infections to map areas for intervention. This ‘gold standard’ has low sensitivity at low infection intensities. The urine point-of-care circulating cathodic antigen test (POC-CCA) is potentially more sensitive but how accurately they detect S. mansoni after repeated praziquantel treatments, their suitability for measuring drug efficacy and their correlation with egg counts remain to be fully understood. We compared the accuracies of one to six Kato-Katzs and one POC-CCA for the diagnosis of S. mansoni in primary-school children who have received zero to ten praziquantel treatments. We determined the impact each diagnostic approach may have on monitoring and evaluation (M&E) and drug-efficacy findings.

Method/Principle Findings

In a high S. mansoni endemic area of Uganda, three days of consecutive stool samples were collected from primary school-aged children (six - 12 years) at five time-points in year one: baseline, one-week-post-, four-weeks-post-, six-months-post-, and six-months-one-week-post-praziquantel and three time-points in years two and three: pre-, one-week-post- and four-weeks-post-praziquantel-treatment/retreatment (n = 1065). Two Kato-Katzs were performed on each stool. In parallel, one urine sample was collected and a single POC-CCA evaluated per child at each time-point in year one (n = 367). At baseline, diagnosis by two Kato-Katzs (sensitivity = 98.6%) or one POC-CCA (sensitivity = 91.7%, specificity = 75.0%) accurately predicted S. mansoni infections. However, one year later, a minimum of three Kato-Katzs, and two years later, five Kato-Katzs were required for accurate diagnosis (sensitivity >90%) and drug-efficacy evaluation. The POC-CCA was as sensitive as six Kato-Katzs four-weeks-post and six-months-post-treatment, if trace readings were classified as positive.

Conclusions/Significance

Six Kato-Katzs (two/stool from three stools) and/or one POC-CCA are required for M&E or drug-efficacy studies. Although unable to measure egg reduction rates, one POC-CCA appears to be more sensitive than six Kato-Katzs at four-weeks-post-praziquantel (drug efficacy) and six-months-post-praziquantel (M&E).

Schistosomiasis is a parasitic disease infecting over 200 million people. It remains a major public health concern despite treatment of over 120 million people in sub-Saharan Africa alone. Accurate diagnostic methods are essential for monitoring drug efficacy and long-term control program success. The World Health Organization recommends two Kato-Katz thick smears (Kato-Katzs) from a single stool for Schistosoma mansoni diagnosis to map prevalence and areas for control interventions. Although highly specific, Kato-Katzs are thought to be insensitive at low egg counts. The recently refined urine point-of-care circulating cathodic antigen test (POC-CCA) has been proposed as a diagnostic alternative for mapping areas for interventions, and potentially for assessing drug efficacy. Over three years we assessed the accuracy of six Kato-Katzs and a single POC-CCA in detecting infections in Ugandan primary-school children at 11 time points with repeated praziquantel treatments. Our results demonstrate that two Kato-Katzs accurately detect S. mansoni infection pre-treatment, but at least three days of two Kato-Katzs per stool or one POC-CCA are required for annual monitoring and treatment evaluation and/or drug-efficacy studies. One POC-CCA may be more sensitive in measuring S. mansoni prevalence than six Kato-Katzs, but its accuracies for rigorous intensity measures are still to be proven.

Day-to-day fluctuation of point-of-care circulating cathodic antigen test scores and faecal egg counts in children infected with Schistosoma mansoni in Ethiopia

Background

Determining the variation of circulating cathodic antigen (CCA) in urine and egg counts variation in stool between days in Schistosoma mansoni (S. mansoni) infected individuals is vital to decide whether or not to rely on a single-sample test for diagnosis of Schistosomiasis. In this study, the magnitude of day-to-day variation in urine-CCA test scores and in faecal egg counts was evaluated in school children in Ethiopia.

Methods

A total of 620 school children (age 8 to 12 years) were examined for S. mansoni infection using double Kato-Katz and single urine-CCA cassette methods (batch 32727) on three consecutive days.

Results

The prevalence of S. mansoni infection was 81.1% based on triple urine-CCA-cassette test and 53.1% based on six Kato-Katz thick smears. Among the study participants, 26.3% showed fluctuation in urine CCA and 32.4% showed fluctuation in egg output. Mean egg count as well as number of cases in each class of intensity and intensity of cassette band color varied over the three days of examination. Over 85% of the children that showed day-to-day variations in status of S. mansoni infection from negative to positive or vice versa by the Kato-Katz and the CCA methods had light intensity of infection. The fluctuation in both the CCA test scores and faecal egg count was not associated with age and sex.

Conclusions

The current study showed day-to-day variation in CCA and Kato-Katz test results of children infected with S. mansoni. This indicates the necessity of more than one urine or stool samples to be collected on different days for more reliable diagnosis of S. mansoni infection in low endemic areas.

Newly established monoclonal antibody diagnostic assays for Schistosoma mansoni direct detection in areas of low endemicity

Background

Current available methods for diagnosis of schistosomiasis mansoni lack sufficient sensitivity, which results in underreporting of infectious in areas of low endemicity.

Methodology/Principal Findings

We developed three novel diagnostic methodologies for the direct detection of schistosome infection in serum samples. These three new methods were evaluated with positive patients from a low endemicity area in southeast Brazil. The basis of the assay was the production of monoclonal antibodies against the protein backbone of heavily glycosylated Circulating Cathodic Antigen (CCA). The antibodies were also selected for having no specificity to repeating poly-Lewis x units. Assays based on the detection CCA-protein should not encounter a limitation in sensitivity due to a biological background of this particular epitope. Three diagnostic methodologies were developed and validated, (i) Immunomagnetic Separation based on improved incubation steps of non-diluted serum, (ii) Direct Enzyme-linked Immunosorbent Assay and (iii) Fluorescent Microscopy Analysis as a qualitative assay. The two quantitative assays presented high sensitivity (94% and 92%, respectively) and specificity (100%), equivalent to the analysis of 3 stool samples and 16 slides by Kato-Katz, showing promising results on the determination of cure.

Conclusions/Significance

The Immunomagnetic Separation technique showed excellent correlation with parasite burden by Cohen coefficient. The qualitative method detected 47 positive individuals out of 50 with the analysis of 3 slides. This easy-to-do method was capable of discriminating positive from negative cases, even for patients with low parasite burden.

Prevalence of schistosome antibodies with hepatosplenic signs and symptoms among patients from Kaoma, Western Province, Zambia

Background

Schistosomiasis is a major cause of morbidity and mortality, with over 200 million people infected worldwide. Eighty-five percent of cases are in Africa. The hepatosplenic form develops over time by an immune reaction to trapped Schistosoma mansoni eggs in the portal system leading to liver fibrosis, portal hypertension and oesophageal varices. Most patients presenting to the University Teaching Hospital in Lusaka with oesophageal varices, come from Western province, but no formal studies have been carried out in this area assessing the burden of hepatosplenic pathology. We aimed to define the extent of the problem in Kaoma district, western Zambia, and to correlate signs and symptoms with serology.

Findings

A symptom questionnaire, demographic survey and physical examination was conducted amongst patients presenting to Kaoma district outpatient clinics. To assess the prevalence of Schistosoma mansoni infections, blood was collected and screened for the presence of Schistosoma antibodies using Enzyme linked immunosorbent assay (ELISA). Of the 110 patients screened, 97 (88%) were ELISA positive. Forty-six percent (51/110) reported haematochezia and 7% experienced haematemesis (8/110). On physical examination 27% (30/110) hepatomegaly and 17% (30/110) splenomegaly was observed amongst participants but there were few correlations between serology and signs/symptoms. On questioning 68% (75/110) of participants knew nothing about schistosomiasis transmission.

Conclusions

Our serological and clinical data indicate a very heavy burden of schistosomiasis-related portal hypertension. Our evidence highlights a need for mass treatment in Kaoma to address and prevent extensive pathology of hepatosplenic schistosomiasis. Safe water and health education throughout Western Province are clearly also important.