The validity of serologic tests for Trypanosoma cruzi and the effectiveness of transfusional screening strategies in a hyperendemic region

Cardiac involvement in Chagas disease and African trypanosomiasis

Trypanosomiases are diseases caused by various species of protozoan parasite in the genus Trypanosoma, each presenting with distinct clinical manifestations and prognoses. Infections can affect multiple organs, with Trypanosoma cruzi predominantly affecting the heart and digestive system, leading to American trypanosomiasis or Chagas disease, and Trypanosoma brucei primarily causing a disease of the central nervous system known as human African trypanosomiasis or sleeping sickness. In this Review, we discuss the effects of these infections on the heart, with particular emphasis on Chagas disease, which continues to be a leading cause of cardiomyopathy in Latin America. The epidemiology of Chagas disease has changed substantially since 1990 owing to the emigration of over 30 million Latin American citizens, primarily to Europe and the USA. This movement of people has led to the global dissemination of individuals infected with T. cruzi. Therefore, cardiologists worldwide must familiarize themselves with Chagas disease and the severe, chronic manifestation - Chagas cardiomyopathy - because of the expanded prevalence of this disease beyond traditional endemic regions.

Chagas disease: Performance analysis of immunodiagnostic tests anti-Trypanosoma cruzi in blood donors with inconclusive screening results

Background

The screening ofTrypanosoma cruzi-infected blood donors using two serological techniques frequently leads to conflicting results. This fact prompted us to evaluate the diagnostic performance of four “in-house” immunodiagnostic tests and two commercially available enzyme-linked immunosorbent assays (ELISAs).

Material and Methods

One hundred and seventy-nine blood donors, whose screening for Chagas disease was doubtful, underwent three in-house ELISAs, one in-house immunoblotting test (TESA-blot), and two commercial ELISAs (bioMérieux and Wiener) in an attempt to define the presence or absence of infection. Simultaneously, 29 donors with previous positive results from three conventional serological tests and 30 donors with constant negative results were evaluated.

Results

The ELISA-Wiener showed the highest rate in sensitivity (98.92%) and the ELISA-bioMérieux, the highest specificity (99.45%), followed by the TESA-blot, which showed superior performance, with lower false-negative (2.18%) and false-positive (1.12%) rates. In series, the combination composed of the TESA-blot and ELISA-bioMérieux showed slightly superior performance, with trifunctional protein deficiency (TFP) = 0.01%.

Conclusion

Our study confirms the high sensitivity and specificity of commercial kits. To confirm the presence or absence of T. cruzi infection, the combination of TESA-blot and ELISA-bioMérieux may be suggested as the best alternative. Individually, the TESA-blot performed the closest to the gold standard; however, it is not commercially available.

Plasma-based COVID-19 treatments in low- and middle-income nations pose a high risk of an HIV epidemic

Convalescent plasma therapy holds promise as a transient treatment for COVID-19. Yet, blood products are important sources of HIV infection in low- and middle-income nations. Great care must be taken to prevent plasma therapy from fueling HIV epidemics in the developing world.

Trypanosoma cruzi infection in transfusion medicine

INTRODUCTION

Infection by Trypanosoma cruzi is challenging to blood bank supplies in terms of accurate diagnosis, mostly due to its clinical complexity. Infected individuals may remain asymptomatic for years, albeit they may have circulating parasites potentially transferable to eventual receptors of a transfusion.

OBJECTIVE

Although risk donors are systematically excluded through a survey, an important residual risk for transmission remains, evidencing the need to implement additional actions for the detection of T. cruzi in blood banks.

METHOD

A review of the scientific literature is presented with the objective of identifying relevant publications on this subject.

RESULTS

We discuss the diagnostic considerations of this chronic infection on transfusion medicine and some recent advances in the processing of blood and derivatives units.

CONCLUSION

Finally, recommendations are made on how the transmission of T. cruzi can be avoided through the implementation of better diagnostic and pathogen control measures at blood banks.

High sensitivity and reproducibility of in-house ELISAs using different genotypes of Trypanosoma cruzi

The adequate choice of Trypanosoma cruzi strains as antigen source for the diagnosis of Chagas disease is still controversial due to differences in terms of accuracy reported between different diagnostic tests. In this study was determined if the genetic variability between different genotypes of T. cruzi (TcI, TcII and TcIV) affect the final diagnosis of Chagas disease. The sensitivity and specificity index of in-house ELISA tests prepared with different T. cruzi strains were evaluated with chagasic and non-chagasic control sera and using the TESA-blot as a reference test. The results of this study revealed that the sensitivity index did not vary, with percentages of 100% for all strains in both tests. However, the specificity index for ELISA tests showed differences between 92% and 98%, but were reduced to 78%-89% when Leishmania-positive sera were included. All ELISAs and TESA-blot prepared with different antigens and the recombinant Wiener test were challenged in an endemic community for Chagas disease in Panama. Both ELISAs and TESA-blot recognized the same positive sera, corroborating the sensitivity indexes (100%) found with the control sera. The TESA-blot maintained the specificity index of 100% and did not display false positives. However, the recombinant Wiener test decreased its sensitivity to 81.25%.

[Costs of Chagas' disease screening test in blood donors in two Colombian blood banks, 2015]

INTRODUCTION

Transfusion is a mechanism of transmission of Chagas' disease. There are no studies on the costs of the screening test in Colombian blood banks.

OBJECTIVE

To estimate the costs of the screening test for Chagas' disease among blood donors in two Colombian blood banks, 2015.

MATERIALS AND METHODS

We conducted a micro-costing study from the perspective of the health care provider to estimate the cost of Chagas' disease testing in two blood banks, Banco de Sangre de la Cruz Roja, Seccional Bolívar, and Banco de Sangre del Hospital de Yopal, Casanare, taking into account four cost categories: 1) Administrative costs: public services and insurance costs were calculated based on the blood bank area in square meters; 2) capital costs: building and equipment costs that were annualized using a 3% discount rate and a lifespan of 20 years for building and five for equipment; 3) costs of Chagas' disease test materials and reagents adjusted by blood bank production level, and 4) costs of staff in charge of Chagas' disease test processing. The costs of transfusion bagsand immunohematology tests are also reported.

RESULTS

The cost of Chagas' disease test in the blood bank of Seccional Bolívar was COP$ 37,804 (USD$ 12), and the blood bag and immunohematology test costs were COP$ 25,941 (USD$ 8.2) and COP$ 6,800 (USD$ 2.2), respectively. In the blood bank of Yopal, Casanare, the costs were COP$ 77,384 (USD$ 24.6), COP$ 30,141 (USD$ 9.6) and COP$ 12,627 (USD$ 4), respectively. Personnel cost accounted for the highest percentage of the total cost for both blood banks (47.5% in Seccional Bolívar, and 55.7% in Yopal, Casanare).

CONCLUSION

Our results are an important input for the planning of services and cost-effectiveness studies for screening tests for Chagas' disease in Colombian blood banks.

Usefulness of FC-TRIPLEX Chagas/Leish IgG1 as confirmatory assay for non-negative results in blood bank screening of Chagas disease

A relevant issue in Chagas disease serological diagnosis regards the requirement of using several confirmatory methods to elucidate the status of non-negative results from blood bank screening. The development of a single reliable method may potentially contribute to distinguish true and false positive results. Our aim was to evaluate the performance of the multiplexed flow-cytometry anti-T. cruzi/Leishmania IgG1 serology/(FC-TRIPLEX Chagas/Leish IgG1) with three conventional confirmatory criteria (ELISA-EIA, Immunofluorescence assay-IIF and EIA/IIF consensus criterion) to define the final status of samples with actual/previous non-negative results during anti-T. cruzi ELISA-screening in blood banks. Apart from inconclusive results, the FC-TRIPLEX presented a weak agreement index with EIA, while a strong agreement was observed when either IIF or EIA/IIF consensus criteria were applied. Discriminant analysis and Spearman's correlation further corroborates the agreement scores. ROC curve analysis showed that FC-TRIPLEX performance indexes were higher when IIF and EIA/IIF consensus were used as a confirmatory criterion. Logistic regression analysis further demonstrated that the probability of FC-TRIPLEX to yield positive results was higher for inconclusive results from IIF and EIA/IIF consensus. Machine learning tools illustrated the high level of categorical agreement between FC-TRIPLEX versus IIF or EIA/IIF consensus. Together, these findings demonstrated the usefulness of FC-TRIPLEX as a tool to elucidate the status of non-negative results in blood bank screening of Chagas disease.

Does my patient have chronic Chagas disease? Development and temporal validation of a diagnostic risk score

INTRODUCTION

With the globalization of Chagas disease, unexperienced health care providers may have difficulties in identifying which patients should be examined for this condition. This study aimed to develop and validate a diagnostic clinical prediction model for chronic Chagas disease.

METHODS

This diagnostic cohort study included consecutive volunteers suspected to have chronic Chagas disease. The clinical information was blindly compared to serological tests results, and a logistic regression model was fit and validated.

RESULTS

The development cohort included 602 patients, and the validation cohort included 138 patients. The Chagas disease prevalence was 19.9%. Sex, age, referral from blood bank, history of living in a rural area, recognizing the kissing bug, systemic hypertension, number of siblings with Chagas disease, number of relatives with a history of stroke, ECG with low voltage, anterosuperior divisional block, pathologic Q wave, right bundle branch block, and any kind of extrasystole were included in the final model. Calibration and discrimination in the development and validation cohorts (ROC AUC 0.904 and 0.912, respectively) were good. Sensitivity and specificity analyses showed that specificity reaches at least 95% above the predicted 43% risk, while sensitivity is at least 95% below the predicted 7% risk. Net benefit decision curves favor the model across all thresholds.

CONCLUSIONS

A nomogram and an online calculator (available at http://shiny.ipec.fiocruz.br:3838/pedrobrasil/chronic_chagas_disease_prediction/) were developed to aid in individual risk estimation.

Cost-Effectiveness of Blood Donation Screening for Trypanosoma cruzi in Mexico

An estimated 2 million inhabitants are infected with Chagas disease in Mexico, with highest prevalence coinciding with highest demographic density in the southern half of the country. After vector-borne transmission, Trypanosoma cruzi is principally transmitted to humans via blood transfusion. Despite initiation of serological screening of blood donations or donors for T. cruzi since 1990 in most Latin American countries, Mexico only finally included mandatory serological screening nationwide in official Norms in 2012. Most recent regulatory changes and segmented blood services in Mexico may affect compliance of mandatory screening guidelines. The objective of this study was to calculate the incremental cost-effectiveness ratio for total compliance of current guidelines from both Mexican primary healthcare and regular salaried worker health service institutions: the Secretary of Health and the Mexican Institute for Social Security. We developed a bi-modular model to analyze compliance using a decision tree for the most common screening algorithms for each health institution, and a Markov transition model for the natural history of illness and care. The incremental cost effectiveness ratio based on life-years gained is US$ 383 for the Secretary of Health, while the cost for an additional life-year gained is US$ 463 for the Social Security Institute. The results of the present study suggest that due to incomplete compliance of Mexico’s national legislation during 2013 and 2014, the MoH has failed to confirm 15,162 T. cruzi infections, has not prevented 2,347 avoidable infections, and has lost 333,483 life-years. Although there is a vast difference in T. cruzi prevalence between Bolivia and Mexico, Bolivia established mandatory blood screening for T.cruzi in 1996 and until 2002 detected and discarded 11,489 T. cruzi -infected blood units and prevented 2,879 potential infections with their transfusion blood screening program. In the first two years of Mexico’s mandated program, the two primary institutions failed to prevent due to incomplete compliance more potential infections than those gained from the first five years of Bolivia’s program. Full regulatory compliance should be clearly understood as mandatory for the sake of blood security, and its monitoring and analysis in Mexico should be part of the health authority’s responsibility.

Chagas disease continues to be a neglected disease in Mexico and Latin-American. Although an estimated 96% of Trypanosoma cruzi transmission to humans occurs via 32 triatomine vector species, the only transmission prevention in Mexico has been sparse and based on heterogeneous blood donation screening. Despite mandating serological screening of blood donations or donors for T. cruzi since 1990 in most Latin American countries, Mexico only finally included mandatory serological screening nationwide in official Norms in 2012. In 2005, a survey of blood donor centers in Mexico was conducted to compare T. cruzi prevalence in donations with that of Mexican migrants in the US. Since there was little coincidence between data from that survey and official screening or confirmed case rates, and screening for the social security system only initiated in 2010, the objective of this study was to calculate the incremental cost-effectiveness ratio for total compliance of current guidelines from both Mexican primary healthcare (the Secretary of Health) and regular salaried worker health services (the Mexican Institute for Social Security). A bi-modular model to analyze compliance was developed using a decision tree for the most common documented screening algorithms for the two principal health institution, and a Markov transition model for the natural history of illness and care. The incremental cost effectiveness ratio based on life-years gained is US$ 383 for the Secretary of Health (MoH), while the cost for an additional life-year gained is US$ 463 for the Social Security Institute (IMSS). Using survey compliance data for MoH, and that published by IMSS, failure to detect current infections, to avoid new infections, and life-years lost were calculated for 2013 and 2014 for both institutions. The MoH has failed to confirm 15,162 T. cruzi infections, did not prevent 2,347 avoidable infections, and lost 333,483 life-years over the two year period. Full regulatory compliance should be mandatory and timely monitoring should be part of the health authority’s responsibilities for the sake of blood security in Mexico.

Chronic Chagas Disease Diagnosis: A Comparative Performance of Commercial Enzyme Immunoassay Tests

There is a significant heterogeneity in reported performance of serological assays for Chagas disease diagnosis. The conventional serology testing in laboratory diagnosis and in blood banks is unsatisfactory because of a high number of inconclusive and misclassified results. We aimed to assess the quality of four commercially available enzyme-linked immunosorbent assay tests for their ability to detect Trypanosoma cruzi antibodies in 685 sera samples. Cross-reactivity was assessed by using 748 sera from patients with unrelated diseases. Initially, we found that the reactivity index against T. cruzi antigen was statistically higher in sera from Chagas disease patients compared with those from non-chagasic patients, supporting the notion that all evaluated tests have a good discriminatory ability toward the diagnosis of T. cruzi infection in patients in the chronic phase of the disease. Although all tests were similarly sensitive for diagnosing T. cruzi infection, there were significant variations in terms of specificity and cross-reactivity among them. Indeed, we obtained divergent results when testing sera from patient with unrelated diseases, particularly leishmaniasis, with the levels of cross-reactivity being higher in tests using whole T. cruzi extracts compared with those using recombinant proteins. Our data suggest that all four tests may be used for the laboratory diagnosis and routine blood screening diagnose for Chagas disease. We also emphasize that, despite their general good performance, caution is needed when analyzing the results when these tests are performed in areas where other diseases, particularly leishmaniasis, are endemic.

Commercial enzyme-linked immunosorbent assay versuspolymerase chain reaction for the diagnosis of chronic Chagas disease: a systematic review and meta-analysis

Chronic Chagas disease diagnosis relies on laboratory tests due to its clinical characteristics. The aim of this research was to review commercial enzyme-linked immunosorbent assay (ELISA) and polymerase chain reaction (PCR) diagnostic test performance. Performance of commercial ELISA or PCR for the diagnosis of chronic Chagas disease were systematically searched in PubMed, Scopus, Embase, ISI Web, and LILACS through the bibliography from 1980-2014 and by contact with the manufacturers. The risk of bias was assessed with QUADAS-2. Heterogeneity was estimated with the I2 statistic. Accuracies provided by the manufacturers usually overestimate the accuracy provided by academia. The risk of bias is high in most tests and in most QUADAS dimensions. Heterogeneity is high in either sensitivity, specificity, or both. The evidence regarding commercial ELISA and ELISA-rec sensitivity and specificity indicates that there is overestimation. The current recommendation to use two simultaneous serological tests can be supported by the risk of bias analysis and the amount of heterogeneity but not by the observed accuracies. The usefulness of PCR tests are debatable and health care providers should not order them on a routine basis. PCR may be used in selected cases due to its potential to detect seronegative subjects.

Chagas disease in the immunosuppressed patient

This review addresses relevant aspects of Chagas disease in the immunocompromised host. Chagas disease--one of the world's most neglected diseases-has become a global public health concern. Novel transmission modalities, such as organ transplantation, evidence of parasite persistence in chronically infected individuals--with the potential for reactivation under immunosuppression--and the prolonged survival of immunosuppressed patients call for an appraisal of the disease in this particular setting. The management and outcome of solid organ transplantation in the infected recipient with special focus on heart transplantation is addressed. The guidelines for management and the outcome of the recipients of organs from infected donors are discussed, and comments on haematopoietic stem cell transplantation are included. Finally, Chagas disease in other situations of impairment of the immune system, such as HIV/AIDS and autoimmune diseases, are considered. Immunosuppression has become an increasingly frequent condition that might modify the natural history of Trypanosoma cruzi infection. A number of strategies are available for Chagas disease management in the immunosuppressed patient. First, according to recent recommendations from the health authorities in Argentina, most infected patients would benefit from being treated at diagnosis. This has not been validated for patients with different immunosuppressive disorders. A different strategy would involve treating only patients with documented reactivation (either parasitaemia or clinical manifestations). These different approaches are discussed. To reach a diagnosis of parasitaemia, monitoring is essential, either with conventional methods or with molecular techniques that are not yet available in all centres. Collaborative studies are needed to improve the level of evidence, which will allow for better guidelines.

Conventional serological performance in diagnosis of Chagas’ disease in southern Brazil

Results of Chagas’ disease diagnosis show disagreement. The aim of this study was to compare commercial tests for Chagas’ disease serodiagnosis in southern Brazil. A total of 161 samples were evaluated. Three enzyme-linked immunosorbent assays, one indirect hemagglutination and one indirect immunofluorescence were assessed. Trypomastigote excreted-secreted antigen-blot was a confirmatory method. From 161 samples, 65.84% were positive in all tests, while 34.16% presents mismatch result in at least one of the tests. All techniques tested presented false-positive and/or false-negative results as follows: Enzyme-linked immunosorbent assay 1 had more false-positive results (lower specificity), indirect immunofluorescence had the highest rate of false-negative results (lower sensitivity), enzyme-linked immunosorbent assays had fewer false-negative results (higher sensitivity), while indirect hemagglutination showed no false-positive result (higher specificity). Knowing the characteristics of techniques make it possible to combine them and obtain more reliable diagnosis. Therefore, it seems useful to combine techniques for diagnosing this infection.

Use of Individual-level Covariates to Improve Latent Class Analysis of Trypanosoma Cruzi Diagnostic Tests

Statistical methods such as latent class analysis can estimate the sensitivity and specificity of diagnostic tests when no perfect reference test exists. Traditional latent class methods assume a constant disease prevalence in one or more tested populations. When the risk of disease varies in a known way, these models fail to take advantage of additional information that can be obtained by measuring risk factors at the level of the individual. We show that by incorporating complex field-based epidemiologic data, in which the disease prevalence varies as a continuous function of individual-level covariates, our model produces more accurate sensitivity and specificity estimates than previous methods. We apply this technique to a simulated population and to actual Chagas disease test data from a community near Arequipa, Peru. Results from our model estimate that the first-line enzyme-linked immunosorbent assay has a sensitivity of 78% (95% CI: 62-100%) and a specificity of 100% (95% CI: 99-100%). The confirmatory immunofluorescence assay is estimated to be 73% sensitive (95% CI: 65-81%) and 99% specific (95% CI: 96-100%).

Sensitivity and specificity of an operon immunochromatographic test in serum and whole-blood samples for the diagnosis of Trypanosoma cruzi infection in Spain, an area of nonendemicity

Trypanosoma cruzi infection is an imported parasitic disease in Spain, and the majority of infected individuals are in the chronic phase of the disease. This study evaluated the sensitivity and specificity of the Operon immunochromatographic test (ICT-Operon; Simple Stick Chagas and Simple Chagas WB [whole blood]; Operon S.A., Spain) for different biological samples. Well-characterized serum samples were obtained from chagasic patients (n = 63), nonchagasic individuals (n = 95), visceral leishmaniasis patients (n = 38), and malaria patients (n = 55). Noncharacterized specimens were obtained from Latin American immigrants and individuals at risk with a clinical and/or epidemiological background: these specimens were recovered serum or plasma samples (n = 450), whole peripheral blood (n = 94), and capillary blood (n = 282). The concordance of the results by enzyme-linked immunosorbent assay and indirect immunofluorescence test was considered to be the "gold standard" for diagnosis. Serum and plasma samples were analyzed by Stick Chagas, and whole blood was analyzed by Simple Chagas WB. The sensitivity and specificity of the ICT-Operon in well-characterized samples were 100% and 97.9%, respectively. No cross-reactivity was found with samples obtained from visceral leishmaniasis patients. In contrast, a false-positive result was obtained in 27.3% of samples from malaria patients. The sensitivities of the rapid test in noncharacterized serum or plasma, peripheral blood, and capillary blood samples were 100%, 92.1%, and 86.4%, respectively, while the specificities were 91.6%, 93.6%, and 95% in each case. ICT-Operon showed variable sensitivity, depending on the kind of sample, performing better when serum or plasma samples were used. It could therefore be used for serological screening combined with any other conventional test.

A field trial of alternative targeted screening strategies for Chagas disease in Arequipa, Peru

BACKGROUND

Chagas disease is endemic in the rural areas of southern Peru and a growing urban problem in the regional capital of Arequipa, population ∼860,000. It is unclear how to implement cost-effective screening programs across a large urban and periurban environment.

METHODS

We compared four alternative screening strategies in 18 periurban communities, testing individuals in houses with 1) infected vectors; 2) high vector densities; 3) low vector densities; and 4) no vectors. Vector data were obtained from routine Ministry of Health insecticide application campaigns. We performed ring case detection (radius of 15 m) around seropositive individuals, and collected data on costs of implementation for each strategy.

RESULTS

Infection was detected in 21 of 923 (2.28%) participants. Cases had lived more time on average in rural places than non-cases (7.20 years versus 3.31 years, respectively). Significant risk factors on univariate logistic regression for infection were age (OR 1.02; p = 0.041), time lived in a rural location (OR 1.04; p = 0.022), and time lived in an infested area (OR 1.04; p = 0.008). No multivariate model with these variables fit the data better than a simple model including only the time lived in an area with triatomine bugs. There was no significant difference in prevalence across the screening strategies; however a self-assessment of disease risk may have biased participation, inflating prevalence among residents of houses where no infestation was detected. Testing houses with infected-vectors was least expensive. Ring case detection yielded four secondary cases in only one community, possibly due to vector-borne transmission in this community, apparently absent in the others.

CONCLUSIONS

Targeted screening for urban Chagas disease is promising in areas with ongoing vector-borne transmission; however, these pockets of epidemic transmission remain difficult to detect a priori. The flexibility to adapt to the epidemiology that emerges during screening is key to an efficient case detection intervention. In heterogeneous urban environments, self-assessments of risk and simple residence history questionnaires may be useful to identify those at highest risk for Chagas disease to guide diagnostic efforts.

Performance of six diagnostic tests to screen for Chagas disease in blood banks andprevalence of Trypanosoma cruzi infection among donors with inconclusive serologyscreening based on the analysis of epidemiological variables

OBJECTIVE

The frequent occurrence of inconclusive serology in blood banks and the absence of a gold standard test for Chagas'disease led us to examine the efficacy of the blood culture test and five commercial tests (ELISA, IIF, HAI, c-ELISA, rec-ELISA) used in screening blood donors for Chagas disease, as well as to investigate the prevalence of Trypanosoma cruzi infection among donors with inconclusive serology screening in respect to some epidemiological variables.

METHODS

To obtain estimates of interest we considered a Bayesian latent class model with inclusion of covariates from the logit link.

RESULTS

A better performance was observed with some categories of epidemiological variables. In addition, all pairs of tests (excluding the blood culture test) presented as good alternatives for both screening (sensitivity > 99.96% in parallel testing) and for confirmation (specificity > 99.93% in serial testing) of Chagas disease. The prevalence of 13.30% observed in the stratum of donors with inconclusive serology, means that probably most of these are non-reactive serology. In addition, depending on the level of specific epidemiological variables, the absence of infection can be predicted with a probability of 100% in this group from the pairs of tests using parallel testing.

CONCLUSION

The epidemiological variables can lead to improved test results and thus assist in the clarification of inconclusive serology screening results. Moreover, all combinations of pairs using the five commercial tests are good alternatives to confirm results.

[Chagas disease and blood transfusion: an emerging issue in non-endemic countries]

Chagas disease or American human trypanosomiasis, is a parasitic disease due to Trypanosoma cruzi, which is endemic in Latin America. The parasite is transmitted by haematophagous vectors from reduviidae family. In some patients, the parasite is responsible for severe complications such as cardiac manifestations, gastrointestinal involvement and neurologic disease. Imported Chagas disease by immigration in non-endemic countries poses the threat of the infection transmission by blood transfusion. In order to prevent this risk, the French Blood Services (EFS) introduced systematic screening of at-risk blood donors for anti-T. cruzi antibodies, in May 2007. The concerned donors are people originating from an endemic area, donors with mothers originating from such an area and individuals who had lived in or travelled to endemic areas. Donors were screened with two different Elisas simultaneously: one Elisa using purified parasite lysate antigens and the second one composed of recombinant antigens. Positive results and discrepant results were further assayed with an immunofluorescence assay. A seroprevalence assay was performed in the 17 French blood centres after an 18-month testing period from May 2007 to December 2008. During this period 4,637,479 million donations were collected. Out of these 163,740 donations were tested (3.5%). The prevalence of anti-T. cruzi antibodies was one in 32,800 donations. Five positive donors were identified. All of them were originating from endemic areas. A rate of 0.85% indeterminate results was found. Screening strategy revision was decided to reduce the number of donors unnecessarily deferred.

Is SELDI-TOF a valid tool for diagnostic biomarkers?

The genome revolution is providing fresh insights into host and parasite genomes, and new tools are becoming available for examining host-parasite interactions at the proteome level. Technologies such as surface-enhanced laser desorption/ionization time-of-flight (SELDI-TOF) mass spectrometry (MS) can be applied to discover biomarkers (alterations in both host and parasite proteomes) associated with parasitic diseases. Such biomarkers can represent host proteins, fragments of host proteins or parasite proteins that appear in body fluids or tissues following infection. Individual biomarkers or biomarker patterns not only have diagnostic utility (e.g. in active disease, prognosis, tests of cure) but can also provide unique insights into the mechanisms underlying host responses and pathogenesis.

ELISA versus PCR for diagnosis of chronic Chagas disease: systematic review and meta-analysis

Background

Most current guidelines recommend two serological tests to diagnose chronic Chagas disease. When serological tests are persistently inconclusive, some guidelines recommend molecular tests. The aim of this investigation was to review chronic Chagas disease diagnosis literature and to summarize results of ELISA and PCR performance.

Methods

A systematic review was conducted searching remote databases (MEDLINE, LILACS, EMBASE, SCOPUS and ISIWeb) and full texts bibliography for relevant abstracts. In addition, manufacturers of commercial tests were contacted. Original investigations were eligible if they estimated sensitivity and specificity, or reliability -or if their calculation was possible - of ELISA or PCR tests, for chronic Chagas disease.

Results

Heterogeneity was high within each test (ELISA and PCR) and threshold effect was detected only in a particular subgroup. Reference standard blinding partially explained heterogeneity in ELISA studies, and pooled sensitivity and specificity were 97.7% [96.7%-98.5%] and 96.3% [94.6%-97.6%] respectively. Commercial ELISA with recombinant antigens studied in phase three investigations partially explained heterogeneity, and pooled sensitivity and specificity were 99.3% [97.9%-99.9%] and 97.5% [88.5%-99.5%] respectively. ELISA's reliability was seldom studied but was considered acceptable. PCR heterogeneity was not explained, but a threshold effect was detected in three groups created by using guanidine and boiling the sample before DNA extraction. PCR sensitivity is likely to be between 50% and 90%, while its specificity is close to 100%. PCR reliability was never studied.

Conclusions

Both conventional and recombinant based ELISA give useful information, however there are commercial tests without technical reports and therefore were not included in this review. Physicians need to have access to technical reports to understand if these serological tests are similar to those included in this review and therefore correctly order and interpret test results. Currently, PCR should not be used in clinical practice for chronic Chagas disease diagnosis and there is no PCR test commercially available for this purpose. Tests limitations and directions for future research are discussed.

Chagas disease: changes in knowledge and management

More than 100 years after the discovery of human American trypanosomiasis by Carlos Chagas, our knowledge and management of the disease are profoundly changing. Substantial progress made by disease control programmes in most endemic areas contrasts with persisting difficulties in the Gran Chaco region in South America and the recent emergence of the disease in non-endemic areas because of population movements. In terms of pathogenesis, major discoveries have been made about the life cycle and genomics of Trypanosoma cruzi, and the role of the parasite itself in the chronic phase of the disease. From a clinical perspective, a growing number of arguments have challenged the notion of an indeterminate phase, and suggest new approaches to manage patients. New methods such as standardised PCR will be necessary to ensure follow-up of this chronic infection. Although drugs for treatment of Chagas disease are limited, poorly tolerated, and not very effective, treatment indications are expanding. The results of the Benznidazole Evaluation For Interrupting Trypanosomiasis (BENEFIT) trial in 2012 will also help to inform treatment. Mobilisation of financial resources to fund research on diagnosis and randomised controlled trials of treatment are international health priorities.

Chagas cardiomyopathy in the context of the chronic disease transition

BACKGROUND

Patients with Chagas disease have migrated to cities, where obesity, hypertension and other cardiac risk factors are common.

METHODOLOGY/PRINCIPAL FINDINGS

The study included adult patients evaluated by the cardiology service in a public hospital in Santa Cruz, Bolivia. Data included risk factors for T. cruzi infection, medical history, physical examination, electrocardiogram, echocardiogram, and contact 9 months after initial data collection to ascertain mortality. Serology and PCR for Trypanosoma cruzi were performed. Of 394 participants, 251 (64%) had confirmed T. cruzi infection by serology. Among seropositive participants, 109 (43%) had positive results by conventional PCR; of these, 89 (82%) also had positive results by real time PCR. There was a high prevalence of hypertension (64%) and overweight (body mass index [BMI] >25; 67%), with no difference by T. cruzi infection status. Nearly 60% of symptomatic congestive heart failure was attributed to Chagas cardiomyopathy; mortality was also higher for seropositive than seronegative patients (p = 0.05). In multivariable models, longer residence in an endemic province, residence in a rural area and poor housing conditions were associated with T. cruzi infection. Male sex, increasing age and poor housing were independent predictors of Chagas cardiomyopathy severity. Males and participants with BMI

CONCLUSIONS

Chagas cardiomyopathy remains an important cause of congestive heart failure in this hospital population, and should be evaluated in the context of the epidemiological transition that has increased risk of obesity, hypertension and chronic cardiovascular disease.

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Key Words Collapse

MESH Headings

• Adolescent
• Adult
• Aged
• Aged, 80 and over
• Antibodies, Protozoan/blood
• Bolivia/epidemiology
• Chagas Cardiomyopathy/complications
• Chagas Cardiomyopathy/epidemiology
• Chagas Cardiomyopathy/mortality
• Chagas Cardiomyopathy/pathology
• Chronic Disease
• DNA, Protozoan/blood
• Enzyme-Linked Immunosorbent Assay
• Female
• Heart Failure/epidemiology
• Heart Failure/etiology
• Humans
• Male
• Middle Aged
• Polymerase Chain Reaction
• Prevalence
• Risk Factors
• Trypanosoma cruzi/genetics
• Trypanosoma cruzi/immunology
• Trypanosoma cruzi/isolation & purification
• Young Adult

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Grants

• 5 P50 AI074285 NIAID NIH HHS
• P50 AI074285 NIAID NIH HHS
• R24 TW007988 FIC NIH HHS
• T35 AI065385 NIAID NIH HHS
• 5 T35 AI065385 NIAID NIH HHS
• D43 TW006581 FIC NIH HHS
• R24TW007988 FIC NIH HHS

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Affiliation(s)

Alicia I. Hidron Division of Infectious Diseases, Department of Medicine, Emory University School of Medicine, Atlanta, Georgia, United States of America
Robert H. Gilman Asociacion Benefica PRISMA, Lima, Peru Facultad de Ciencias y Filosofía, Universidad Peruana Cayetano Heredia, Lima, Peru
Juan Justiniano Hospital Universitario Japones, Santa Cruz de la Sierra, Bolivia
Anna J. Blackstock Division of Parasitic Diseases, Centers for Disease Control and Prevention, Atlanta, Georgia, United States of America Atlanta Research and Education Foundation, Decatur, Georgia, United States of America
Carlos LaFuente Hospital Universitario Japones, Santa Cruz de la Sierra, Bolivia
Walter Selum Hospital Universitario Japones, Santa Cruz de la Sierra, Bolivia
Martiza Calderon Facultad de Ciencias y Filosofía, Universidad Peruana Cayetano Heredia, Lima, Peru
Manuela Verastegui Facultad de Ciencias y Filosofía, Universidad Peruana Cayetano Heredia, Lima, Peru
Lisbeth Ferrufino Hospital Universitario Japones, Santa Cruz de la Sierra, Bolivia
Eduardo Valencia Facultad de Ciencias y Filosofía, Universidad Peruana Cayetano Heredia, Lima, Peru
Jeffrey A. Tornheim Mount Sinai School of Medicine, New York, New York, United States of America
Seth O'Neal Oregon Health Sciences University, Portland, Oregon, United States of America
Robert Comer Wake Forest University Health Sciences, Winston-Salem, North Carolina, United States of America
Gerson Galdos-Cardenas Asociacion Benefica PRISMA, Lima, Peru
Caryn Bern Division of Parasitic Diseases, Centers for Disease Control and Prevention, Atlanta, Georgia, United States of America
for the Chagas Disease Working Group in Peru and Bolivia

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Estimation of sensitivity and specificity of several Trypanosoma cruzi antibody assays in blood donors in Argentina

BACKGROUND

The absence of a gold standard test for Trypanosoma cruzi antibodies represents a problem not only for the evaluation of screening tests, but also for appropriate blood donor counseling. The aim of this study was to estimate the sensitivity and specificity of multiple blood donor screening tests for T. cruzi antibodies in Argentina.

STUDY DESIGN AND METHODS

From June 2006 to March 2007 a sample of 1455 blood donors was recruited from two blood banks in Chaco province, an area of Argentina with highly endemic T. cruzi infection. Samples were tested by three epimastigote lysate enzyme immunoassays (EIAs), one recombinant antigen EIA, two indirect hemagglutination assay (IHA) tests, a particle agglutination assay (PA), and a research trans-sialidase inhibition assay (TIA). Sensitivity and specificity were estimated using latent class analysis (LCA).

RESULTS

LCA estimated the consensus prevalence of T. cruzi infection at 24.5%. Interassay correlation was higher among the four EIA tests and TIA compared to IHA tests. Assay sensitivities varied from 96 to 99.7 for different EIAs, 91% for TIA, 84% for PA, and 66 to 74% for IHA tests. Relative to the LCA, assay specificities were from 96% to almost 100%.

CONCLUSION

Based on the comparison of several tests in a large population from an endemic area for T. cruzi infection, our data showed an adequate sensitivity for EIA tests in contrast to PA and IHA assays. The latter tests should no longer be used for blood donor screening.

Eliminating Chagas disease: challenges and a roadmap

Millions of people in Central and Southern America are affected by Chagas disease. Richard Reithinger and colleagues explain the difficulties of elimination and suggest a strategy

A population-based study of the association between Trypanosoma cruzi infection and cognitive impairment in old age (the Bambuí Study)

BACKGROUND

Limited clinical data suggest that chronic Trypanosoma cruzi infection, which causes Chagas' disease (ChD), is associated with cognitive impairment. This study investigated this association in a large population-based sample of older adults.

METHODS

Participants in this cross-sectional study comprised 1,449 persons aged > or = 60 years from a Brazilian endemic area (Bambuí). Cognitive functioning was ascertained by the Mini-Mental State Examination (MMSE), considering its score in percentiles [< or =14 (<5th percentile), 15-22 (5th to <25th) and > or =23]. Hypothesized risk factors were T. cruzi infection, ChD-related electrocardiographic (ECG) abnormalities and use of digoxin medication. Potential confounders included depressive symptoms, smoking, stroke, hemoglobin, HDL cholesterol, blood glucose, systolic blood pressure, and use of psychoactive medication.

RESULTS

The prevalence of T. cruzi infection was 37.6%. There was a graded and independent association between infection and the MMSE score (adjusted odds ratios estimated by ordinal logistic regression = 1.99; 95% CI 1.43-2.76). No significant associations between the MMSE score and ECG abnormalities or digoxin medication use were found.

CONCLUSIONS

This study provides for the first time epidemiological evidence of an association between T. cruzi infection and cognitive impairment which was not mediated by either ChD-related ECG abnormalities or digoxin medication use.

Triagem neonatal para infecção chagásica congênita: aplicação de análise de classe latente para avaliação dos testes diagnósticos

O presente estudo tem como objetivo avaliar os testes sorológicos convencionais usados na triagem neonatal para doença de Chagas, discutindo métodos estatísticos disponíveis. Estudou-se uma amostra aleatória dentre 23.308 recém-nascidos triados para doença de Chagas congênita por meio de três testes: imunoensaioenzimático, imunofluorescência indireta e hemoaglutinação indireta. Os dados obtidos foram analisados por diferentes metodologias estatísticas: a análise de classe latente, o teste Kappa e a análise de sensibilidade relativa. Utilizando a análise de classe latente, a maior sensibilidade foi do imunoensaioenzimático (48,6%), seguido pela imunofluorescência indireta (39,8%) e pela hemoaglutinação indireta (23,2%). O valor Kappa foi 0,496. A razão entre as sensibilidades dos testes imunoensaioenzimático e imunofluorescência indireta foi de 92% [0,74;1,13]. A análise de classe latente não se mostrou adequada para determinação de sensibilidade e especificidade, mas forneceu dados importantes sobre a equivalência dos testes, corroborados pela análise de sensibilidade relativa. Os resultados mostraram que o teste imunoensaioenzimático em sangue-seco pode ser utilizado com a mesma segurança do teste imunofluorescência indireta.

High throughput selection of effective serodiagnostics for Trypanosoma cruzi infection

Background

Diagnosis of Trypanosoma cruzi infection by direct pathogen detection is complicated by the low parasite burden in subjects persistently infected with this agent of human Chagas disease. Determination of infection status by serological analysis has also been faulty, largely due to the lack of well-characterized parasite reagents for the detection of anti-parasite antibodies.

Methods

In this study, we screened more than 400 recombinant proteins of T. cruzi, including randomly selected and those known to be highly expressed in the parasite stages present in mammalian hosts, for the ability to detect anti-parasite antibodies in the sera of subjects with confirmed or suspected T. cruzi infection.

Findings

A set of 16 protein groups were identified and incorporated into a multiplex bead array format which detected 100% of >100 confirmed positive sera and also documented consistent, strong and broad responses in samples undetected or discordant using conventional serologic tests. Each serum had a distinct but highly stable reaction pattern. This diagnostic panel was also useful for monitoring drug treatment efficacy in chronic Chagas disease.

Conclusions

These results substantially extend the variety and quality of diagnostic targets for Chagas disease and offer a useful tool for determining treatment success or failure.

The diagnosis of Trypanosoma cruzi infection (the cause of human Chagas disease) is difficult because the symptoms of the infection are often absent or non-specific, and because the parasites themselves are usually below the level of detection in the infected subjects. Therefore, diagnosis generally depends on the measurement of T. cruzi–specific antibodies produced in response to the infection. However, current methods to detect anti–T. cruzi antibodies are relatively poor. In this study, we have conducted a broad screen of >400 T. cruzi proteins to identify those proteins which are best able to detect anti–T. cruzi antibodies. Using a set of proteins selected by this screen, we were able to detect 100% of >100 confirmed positive human cases of T. cruzi infection, as well as suspect cases that were negative using existing tests. This protein panel was also able to detect apparent changes in infection status following drug treatment of individuals with chronic T. cruzi infection. The results of this study should allow for significant improvements in the detection of T. cruzi infection and better screening methods to avoid blood transfusion–related transmission of the infection, and offer a crucial tool for determining the success or failure of drug treatment and other intervention strategies to limit the impact of Chagas disease.

Trans-sialidase inhibition assay for the detection of Trypanosoma cruzi infection in blood donor samples from Argentina

BACKGROUND AND OBJECTIVES

Conventional serology tests for Trypanosoma cruzi blood banks screening are neither sensitive nor specific enough, and currently no gold standard assay is available. Trans-sialidase inhibition assay (TIA) detects neutralizing antibodies against T. cruzi trans-sialidase. Conventional serology inconclusive, positive and negative blood donor samples were evaluated by employing TIA as a supplementary test.

MATERIALS AND METHODS

Three hundred and twenty-one blood donor samples were tested using a combination of assays. Based on the results of testing, these were divided into a number of groups. All samples were tested by TIA.

RESULTS

In conventional serology inconclusive samples 48.1% were TIA-positive, 1/54 conventional serology positive samples was TIA-negative. All negative samples from donors without epidemiological risks were TIA-negative; 1/48 was positive in those with epidemiological risk.

CONCLUSION

Trans-sialidase inhibition assay application in blood banks may be useful to resolve inconclusive samples, and thus improves donor counseling and allows individual re-entry. The use of TIA in samples from negative conventional test donors but positive epidemiological antecedents may contribute to decrease transfusional risk.

Kinetoplastids: related protozoan pathogens, different diseases

Kinetoplastids are a group of flagellated protozoans that include the species Trypanosoma and Leishmania, which are human pathogens with devastating health and economic effects. The sequencing of the genomes of some of these species has highlighted their genetic relatedness and underlined differences in the diseases that they cause. As we discuss in this Review, steady progress using a combination of molecular, genetic, immunologic, and clinical approaches has substantially increased understanding of these pathogens and important aspects of the diseases that they cause. Consequently, the paths for developing additional measures to control these "neglected diseases" are becoming increasingly clear, and we believe that the opportunities for developing the drugs, diagnostics, vaccines, and other tools necessary to expand the armamentarium to combat these diseases have never been better.

Problems and perspectives for Chagas disease control: in search of a realistic analysis

Chagas disease was an important medical and social problem in almost all of Latin America throughout the twentieth century. It has been combated over a broad swath of this continent over recent decades, with very satisfactory results in terms of vector and transfusional transmission. Today, a surveillance stage still remains to be consolidated, in parallel with appropriate care required for some millions of infected individuals who are today living in endemic and non-endemic areas. Contradictorily, the good results attained have generated excessive optimism and even disregard among health authorities, in relation to this disease and its control. The loss of visibility and priority may be a logical consequence, particularly in Latin American healthcare systems that are still disorganized and overburdened due to insufficiencies of financial and human resources. Consolidation of the victories against Chagas disease is attainable but depends on political will and continual attention from the most consequential protagonists in this struggle, especially the Latin American scientific community.

Prevalence of transfusion-transmitted Chagas Disease among multitransfused patients in Brazil

Background

Blood transfusion has always been an important route for Chagas Disease (CD) transmission. The high prevalence of CD in Latin America and its lifelong asymptomatic clinical picture pose a threat for the safety of the blood supply. The outcome of measures designed to improve transfusion safety can be assessed by evaluating the prevalence of CD among multitransfused patients

Methods

In order to assess the impact of CD control measures on the safety of the blood supply, an observational cross-sectional study was designed to determine the prevalence of CD in 351 highly transfused patients, in which vectorial transmission was excluded. This study compared patients that received transfusion products before (n = 230) and after (n = 121) 1997, when measures to control transfusion-transmitted CD were fully implemented in Brazil.

Results

The study group consisted of 351 patients exposed to high numbers of blood products during their lifetime (median number of units transfused = 51, range 10–2086). A higher prevalence of transfusion-transmitted CD (1.30%) was observed among multitransfused patients that received their first transfusion before 1997, compared with no cases of transfusion-transmitted CD among multitransfused patients transfused after that year. The magnitude of the exposure to blood products was similar among both groups (mean number of units transfused per year of exposure = 25.00 ± 26.46 and 23.99 ± 30.58 respectively; P = 0.75, Mann-Whitney test).

Conclusion

Multiple initiatives aimed to control vector and parental transmission of CD can significantly decrease transfusion-transmitted CD in Brazil. Our data suggest that mandatory donor screening for CD represents the most important measure to interrupt transmission of CD by blood transfusions.

The challenges of Chagas Disease-- grim outlook or glimmer of hope

The authors discuss the key challenges that undermine the control of Chagas disease and that must be urgently addressed to ensure long-term, sustainable control.