Received Jun 30; Accepted Oct 1; Collection date May 1.
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PMCID: PMC PMID:Chagas disease affects an estimated 326 000'347 000 people in the United States and is severely underdiagnosed. Lack of awareness and clarity regarding screening and diagnosis is a key barrier. This article provides straightforward recommendations, with the goal of simplifying identification and testing of people at risk for US healthcare providers.
A multidisciplinary working group of clinicians and researchers with expertise in Chagas disease agreed on 6 main questions, and developed recommendations based on the Grading of Recommendations Assessment, Development and Evaluation (GRADE) methodology, after reviewing the relevant literature on Chagas disease in the United States.
Individuals who were born or resided for prolonged time periods in endemic countries of Mexico and Central and South America should be tested for Trypanosoma cruzi infection, and family members of people who test positive should be screened. Women of childbearing age with risk factors and infants born to seropositive mothers deserve special consideration due to the risk of vertical transmission. Diagnostic testing for chronic T. cruzi infection should be conducted using 2 distinct assays.
Increasing provider-directed screening for T. cruzi infection is key to addressing this neglected public health challenge in the United States.
Keywords: Chagas disease, Trypanosoma cruzi, diagnosis, neglected diseases
This article provides recommendations for screening and diagnosis of Chagas disease in the United States, including identification of the population at risk in community or clinical settings, diagnosis of chronic and congenital infection, and next steps following confirmed diagnosis.
Chagas disease (CD) is a neglected tropical disease of substantial public health importance. In the United States, >300 000 people are estimated to be infected with Trypanosoma cruzi, the protozoan that causes the disease [1, 2]. The vast majority were infected while living in endemic areas of Latin America and are in a chronic phase of the disease. While most remain asymptomatic for life, 20%'30% eventually develop Chagas cardiomyopathy, and up to 10% may suffer damage to the gastrointestinal or nervous systems [3]. CD causes a heavy burden of morbidity and mortality, resulting in an estimated global annual loss of >800 000 disability-adjusted life-years, including >27 000 annually in the United States [4]. Only about 1% of estimated US cases have been identified, usually through blood donor screening [5]. Most people are unaware they are infected with T. cruzi. Provider-directed screening is essential because early diagnosis and treatment can improve outcomes and limit mother-to-child transmission. Screening programs for CD are highly cost-effective [6], but with the current paradigm of limited testing, estimated total annual healthcare costs from CD in the United States exceed $130 000 000 [4]. However, not all US providers are aware of CD [7] and testing poses certain challenges.
The Pan American Health Organization has provided overall guidelines on diagnosis and management of CD [8]. The US Centers for Disease Control and Prevention (CDC) website also provides specific recommendations for healthcare providers [9'11]. Here we examine considerations for screening and diagnosis of CD in the United States.
A group of experts on CD screening and management in the United States, including clinicians, researchers, and public health experts, prepared these recommendations. Group members had previously participated in meetings on challenges in diagnosis of CD. The working group was organized to provide a straightforward, quick-reference tool to facilitate CD testing by primary healthcare providers, hospitals, infectious disease specialists, and laboratories. Diagnostic guidance was constructed via both expert consensus and the Grading of Recommendations Assessment, Development and Evaluation (GRADE) methodology [12]. The group agreed on 6 main questions based on the PICO method (Population, Intervention, Comparison, and Outcome) and divided into subgroups to discuss each and propose initial recommendations, which were then shared and validated within the larger group. Literature searches were conducted on CD screening and prevalence in the United States and the 4 assays that are currently Food and Drug Administration (FDA)-cleared for clinical use (Table 1).
The GRADE methodology provides 2 types of ratings. The strength of the recommendation (strong or conditional, either for or against a recommendation) is based on the public health priority, potential benefit, feasibility of implementation, acceptability to patients, and costs in terms of resources. An additional rating is provided for the quality of available evidence supporting the recommendation (high, moderate, low, very low), which considers previous study designs, effect size, relevance, sources of bias, and other factors. Two key limitations should be noted: (1) the evidence on US CD has significant gaps, and (2) while the GRADE methodology provides a structured, evidence-based framework, this does not completely rule out subjectivity in determining ratings.
1. Screening people who were born or lived for a prolonged period (>6 months) in areas of Mexico, Central or South America with endemic CD can effectively identify new cases (strong, low) (Table 2).
Within the US population, people who were born or lived for a prolonged period in areas with endemic CD in Mexico, Central, or South America are at greatest risk of T. cruzi infection (Table 3). One community-based study of over Latin-American born immigrants living in Los Angeles showed a seroprevalence of 1.24% [16]. Among people who were born or lived for a prolonged period in Latin America, the seroprevalence has been higher still in those with evidence of characteristic findings on electrocardiogram (ECG) including bundle-branch blocks, nonischemic cardiomyopathy, or pacemaker placement [17'20]. This supports the assertion that screening people who were born or lived for a prolonged period in areas with endemic CD'Mexico and Central and South America'is a viable approach to identifying new cases. Generally, people will need to be screened even though they do not exhibit visible signs or symptoms of CD.
2. Screening close (first-degree) relatives of people previously diagnosed with CD can effectively identify new cases (strong, low).
Limited evidence shows a substantial prevalence of T. cruzi infection among close relatives of people previously diagnosed with CD. A Los Angeles study found a prevalence of 7.4% among family members of CD patients [14]. Screening the relatives of people who have been previously diagnosed with the disease is another way to identify individuals with CD. When a patient is confirmed positive, healthcare providers should encourage the patient to advise family members to seek testing. (Contact information for US providers with expertise in CD can be found at https://uschagasnetwork.org/providers).
3. Screening people with documented exposure to triatomines in states with known presence of triatomine species capable of transmitting T. cruzi (conditional, low).
Autochthonous transmission can occur in the United States, with cases reported in at least 8 states as of . Most confirmed or suspected autochthonous cases were detected via screening of blood donors, and often these cases face barriers to obtaining treatment [21, 22]. Triatomines (kissing bugs) have been identified in 29 states in the southern United States and limited studies have shown that most can harbor T. cruzi at varying rates [23, 24]. Some infected triatomines feed on humans, based on the finding of human blood in their gut [24, 25]. Because autochthonous transmission has been demonstrated and naturally infected triatomines reside in the United States, screening people who have highly suspected exposure to triatomines (eg, entomological confirmation of triatomines in the home) in states where the vector is known to reside is a reasonable approach to identifying potential cases of autochthonous CD [26].
4. Travelers with confirmed exposure to triatomines or associated risk factors in regions of Latin America where CD is endemic may be tested to rule out possible T. cruzi infection (conditional, low).
Acquisition of CD is thought to occur rarely among travelers, but evidence is limited. Risk factors for travel-acquired CD include confirmed or suspected exposures to triatomines, staying in a rural setting in housing constructed of mud, adobe, thatch, or other natural materials, and consumption of raw or unpasteurized food or beverages, such as sugar cane extract, guava and bacaba juice, açaí pulp, or palm wine [27]. Such travelers may have nonspecific symptoms including fever, malaise and myalgias; acute CD should be considered in addition to other infectious diseases. We advise travel medicine specialists to consider the risk and include advice on preventive measures for individuals with high-risk travel that might expose them to the T. cruzi vector.
1. Screening women of childbearing age who have lived in a region of Mexico, South or Central America with endemic CD can effectively identify cases and prevent congenital transmission of the disease (strong, moderate).
Congenital transmission of CD from infected mother to unborn child is a potentially important mode of disease transmission in the United States. Several US surveys in pregnant women from high-risk groups have shown a substantial prevalence of T. cruzi infection (Table 4). From a public health perspective, treatment of women before pregnancy can prevent congenital transmission and provide health benefits for the mother [32]. Targeted and universal screening for CD in US mothers is cost-saving for all rates of congenital transmission >0.001% and all levels of maternal prevalence >0.06%, compared with no screening [6].
1. T. cruzi serologic testing should be performed in individuals with epidemiological risk factors who present with the following clinical syndromes:
Electrocardiographic abnormalities suggestive of infection, even in the absence of symptoms. These include first-degree atrioventricular block, premature ventricular contractions, atrial fibrillation, right bundle branch block, left anterior fascicular block, bifascicular block, and low voltage QRS (strong, low)
Bradyarrhythmias (strong, low)
Tachyarrhythmias (atrial fibrillation/ventricular tachycardia), including sudden cardiac death (strong, low)
Regional wall motion abnormalities (particularly basal inferolateral, apical aneurysm) (strong, low)
Thromboembolic phenomenon (strong, low)
Congestive heart failure and/or a reduced ejection fraction (strong, low)
Megacolon/megaesophagus (strong, low).
Screening Latin American-born individuals with the above syndromes for CD has ramifications for the evaluation, treatment, and prognosis of the individual. Because of limited screening for CD in the United States and profound healthcare barriers for the at-risk population, many individuals with CD first receive medical attention after developing a clinical syndrome of the illness. However, estimates suggest <1% of people with signs/symptoms suggestive of CD actually receive CD testing [33]. An estimated 30 000'45 000 people in the United States suffer from CD cardiomyopathy [2]. In 2 small studies of Latin American-born patients with nonischemic cardiomyopathy, 5/39 in a New York hospital and 26/135 in a Los Angeles hospital network were seropositive for T. cruzi infection [19, 20]. Other Los Angeles studies in Latin American-born patients found a prevalence of 7.5% among those with pacemakers and 5.2% in those with conduction abnormalities [17, 18].
Immunosuppressed hosts with acute T. cruzi infection (eg, donor-derived infection) are at risk for severe manifestations such as meningoencephalitis or acute myocarditis. Recipients of blood components, organ, or tissue from an infected donor should be monitored by serial polymerase chain reaction (PCR) in blood weekly during months 1'2, every 2 weeks during months 3'4, monthly during months 5'6 posttransfusion or transplant, then based on the clinical scenario [10].
Immunosuppression in an individual with chronic T. cruzi infection may lead to reactivation, characterized by a return to high levels of parasitemia. In transplant recipients, manifestations of reactivation vary depending on host characteristics and immunosuppressive regimen; reactivation myocarditis can be life threatening. A positive PCR result does not constitute a diagnosis of reactivation, because this occurs in patients with chronic infection in the absence of reactivation. Serial monitoring by quantitative PCR, using a schedule similar to that outlined above, provides early detection of reactivation based on falling cycle threshold (Ct) values, reflecting rising parasite loads [34, 35]. The US CDC provides consultation on the management of patients and acts as a reference laboratory to monitor for reactivation by serial PCR. The most common manifestations of reactivation in human immunodeficiency virus (HIV)-T. cruzi coinfected patients include central nervous system (CNS) mass lesions, with or without meningoencephalitis, and myocarditis. Diagnosis varies depending on the clinical scenario; in CNS reactivation, parasites may be detectable by microscopy or PCR of cerebrospinal fluid.
1. Infants in whom congenital CD is suspected should undergo evaluation using existing CDC-based recommendations (strong, moderate).
Edwards et al [11] provides a comprehensive review of diagnosis and treatment of congenital CD that is summarized below. Infants born to women with suspected or confirmed CD, and infants with clinical features of congenital infection born to women at risk for CD, should undergo evaluation as soon as possible after birth to detect hepatomegaly, splenomegaly, anemia, or thrombocytopenia and, as indicated, pneumonitis, heart failure, cardiac arrhythmia, or meningoencephalitis (Figure 1) [11, 36, 37]. The cure rate for treatment in the first year of infection exceeds 90%, and treatment is well tolerated [36, 38, 39].
If the mother's infection status is unknown, serologic testing for T. cruzi immunoglobulin G (IgG) antibodies should be performed to determine infant risk. Diagnosis of congenital infection relies on detection of motile trypomastigotes through microscopic examination of a wet mount of fresh anticoagulated blood or buffy coat specimen (collected in a microhematocrit tube), detection of parasites on Giemsa-stained blood smears, and/or PCR testing for T. cruzi DNA in whole blood from the infant. This testing is available through the Parasitic Diseases Reference Laboratory at the CDC. Histopathologic examination of the umbilical cord and examination of cerebrospinal fluid in at-risk infants with meningoencephalitis may also reveal the parasite [40]. Because maternal blood contamination has been reported in a small number of infants born to infected mothers, a positive PCR result in an infant should be confirmed by repeat testing (Figure 1). If a second PCR is positive, the diagnosis of congenital CD is confirmed and the infant should undergo clinical evaluation for features of congenital CD (such as cardiac arrhythmias), laboratory evaluation, and initiation of treatment. For mothers who are seropositive for T. cruzi infection whose infants are PCR negative, infants should undergo repeat testing at 4 to 6 weeks of age to confirm absence of infection [40, 41].
Because parasitemia levels can fluctuate, the serologic status of infants born to mothers with chronic CD should be monitored even if the infant has negative PCR results early in life. Transferred maternal IgG antibodies persist in infants for up to 12 months [42, 43]. If an infant first evaluated at 3 months of age or older has a positive CD screening T. cruzi IgG test, performed through a commercial laboratory, repeat screening should be performed when the infant reaches 9 to 12 months of age. If antibody remains detectable, confirmatory serologic testing through CDC is appropriate to establish or exclude congenital infection (Figure 2) [36]. An increase in antibody titer over time after 9 months of age, documented at CDC, indicates congenital infection.
Diagnostic testing for chronic T. cruzi infection should be conducted using 2 distinct assays, based on different antigens or in different formats, following Pan American Health Organization and CDC guidelines. If the results are discordant, a third distinct test should be performed. Confirmed diagnosis requires positive results by at least 2 tests (strong, moderate).
Screening by clinical and public health laboratories in populations with low T. cruzi infection prevalence should be conducted using a high-sensitivity test, bearing in mind the anticipated false-positive rate of (1 ' specificity). Individuals with positive results by the screening test require confirmatory testing as outlined in the above recommendation (strong, moderate).
Confirmation of chronic T. cruzi infection requires positive results by 2 different tests, preferably based on different antigens, to optimize sensitivity and specificity [8]. However, most commercial laboratories in the United States only utilize 1 assay. If positive based on commercial laboratory results, sending samples to CDC for confirmation assures that the criteria of 2 distinct assays is met. More confirmatory testing options may become available in the future. Clinicians should check with their healthcare system's clinical laboratory for current or preferred confirmatory testing options.
Providers can contact CDC with questions about CD (, 404'718'). Requests for CDC testing should be coordinated with the state or local health department.
Four IgG serological tests have FDA clearance for diagnosis of chronic T. cruzi infection (Table 1), 2 are T. cruzi lysate-based enzyme-linked immunoassays (ELISAs; Ortho T. cruzi ELISA and Hemagen Chagas' kit ELISA); a recombinant antigen-based ELISA (Wiener Chagatest Recombinante 3.0); and a recombinant antigen-based immunochromatographic strip test (InBios Chagas Detect Plus). All 4 tests have high manufacturer-reported sensitivity and specificity, but postclearance performance data are sparse, especially in US-resident populations (Supplementary Table 1). In US-based evaluations, the Wiener Chagatest Recombinante 3.0 assay consistently showed high specificity and intermediate sensitivity [13, 29, 44]. Investigations also confirm variation in assay performance by geographic origin of infections, with sensitivity generally highest in specimens from South America, intermediate in Central America, and lowest in those from Mexico, Panama, and southern Peru [13, 44'47]. These differences are often attributed to T. cruzi genetic differences, but do not correlate entirely with the predominant lineages as currently identified [48]. Further diagnostic test evaluations in robust sets of specimens from at-risk US populations are needed to provide an adequate evidence base for recommendations for use of specific assays.
However, prospective parallel testing by multiple assays in population-level screening may be prohibitively expensive. In a serial testing scenario, the population is screened by a single test and only those with positive results receive a second, confirmatory test; when the results are discordant, a third test is used as a tiebreaker. Algorithms should be designed with test performance characteristics in mind; a deliberate choice must be made regarding the acceptable number of missed infections versus the cost of additional testing (and the logistics of having patients return for testing) required to rule out false positives. Figure 3 provides a basic framework of the testing process, from identification of risk factors to diagnostic confirmation.
The lack of a gold standard CD test necessitates multistep serological testing to confirm chronic T. cruzi infection. Discordant test results can be expected due to imperfect test performance and will be a large proportion of total results given CD's overall low prevalence in the United States. When the results of the first 2 assays are discordant, a third test is required to assign a consensus positive or negative status for the presence of IgG antibodies to T. cruzi in the individual.
Diagnostic serologic testing in the United States is primarily available at commercial reference laboratories and CDC. Currently, CDC performs an ELISA (Chagatest Recombinante v0.3.0; Wiener Laboratories) and an immunoblot using trypomastigote excreted-secreted antigens (TESA) when CD serology is requested. If results are discordant, a second sample is requested; if results are again discordant, a third serologic test is run (immunofluorescence assay [IFA] based on slide-fixed epimastigotes) [49, 50]. At CDC, the TESA and IFA assays are laboratory-developed tests and all tests are run under the Clinical Laboratory Improvement Amendments (CLIA). Currently, the FDA does not clear or approve laboratory-developed tests [51], but their validation and performance is reviewed during laboratory inspections to maintain CLIA certification. There are no published diagnostic evaluations for the CDC TESA and IFA tests in infected populations of the United States, but these test formats have been widely used throughout Latin America.
Most testing currently begins with a commercial laboratory, where typically only one IgG assay is used. Commercial laboratories periodically change the tests they employ due to commercial availability, cost, and testing format and performance. To ensure that 2 different serologic assays are used, it will be necessary to confirm which assay is being performed. In general, a sample should then be sent to CDC for confirmation.
1. Even if asymptomatic, individuals who test positive for T. cruzi infection should receive:
Electrocardiogram (strong, high)
Echocardiogram (strong, low)
Chest X-ray, if an echocardiogram is unavailable (conditional, low).
Individuals with T. cruzi infection may have no evidence of organ involvement (indeterminate form) or organ involvement with or without noticeable symptoms. Individuals with any of these forms would be expected to be seropositive. Determining whether the patient has the indeterminate form of CD or has progressed to Chagas cardiomyopathy or other end-organ involvement is important for establishing a treatment plan. A normal echocardiogram and ECG indicate an indeterminate form of CD [52]. In settings where an echocardiogram is not available, a chest X-ray may be considered instead. The ECG should be repeated annually to detect signs of progression to Chagas cardiomyopathy, even in individuals who receive antitrypanosomal treatment [52]. Echocardiogram may be repeated depending on the patient's clinical status. Those with cardiac symptoms and/or abnormalities on 1 or more of the above tests should be referred to a cardiologist for more extensive testing [53]. Patients with immunosuppressive conditions require special consideration due to the risk of reactivation and should be referred to an infectious disease specialist. Patients from southern Cone countries of South America (Argentina, Bolivia, Brazil, Chile, and Paraguay) may be more at risk for gastrointestinal complications. Steps for diagnosis and management of gastrointestinal CD are provided by Pinazo et al [54].
Uncertainties and complexities around current CD testing processes in the United States pose a major barrier to increasing screening coverage, perpetuating a situation where <1% of the estimated population with the disease has been tested. This document provides clear, straightforward guidance to healthcare personnel to facilitate screening and diagnosis of the people at risk, so that they can receive timely and appropriate care. While more research is needed, both on the epidemiology of CD in the United States, including congenital and vector-borne transmission and the burden of disease in specific populations, and on the performance of diagnostic tools in the heterogeneous US patient population, this document presents practical recommendations based on the best information currently available. Ensuring proactive screening of patients will require concerted efforts to increase provider awareness, convey accurate information to the public about CD and its risks, and improve access to and performance of diagnostic technology and tools.
Acknowledgments. The authors thank Susan P. Montgomery, Division of Parasitic Diseases and Malaria of Centers for Disease Control and Prevention (CDC) for invaluable overall guidance and support and immensely helpful comments and suggestions; and Paul Cantey and Barbara Marston, Division of Parasitic Diseases and Malaria of CDC for their comments on the manuscript. Thanks also to Maria Jesús Pinazo, Barcelona Institute of Global Health and Sergio Sosa-Estani and Louise Burrows, Drugs for Neglected Diseases initiative (DNDi) for their suggestions; and Hannah Salem of DNDi for help with logistics. DNDi is grateful to its donors, public and private, who have provided funding to DNDi since its inception in . A full list of DNDi donors can be found at http://www.dndi.org/donors/donors.
Financial support. This work was supported by Drugs for Neglected Diseases Initiative (funding for travel and meetings); the Mundo Sano Foundation (grant number AWD to N. B.); Infectious Diseases Society of America Foundation (grant number AWD to N. B.); Centers for Disease Control and Prevention Parasitic Diseases Branch for Chagas (grant number NU2GGH to P. S., grant number NU2GGH-01-00 to N. H., and grant number NU2GGH-01-00 to D. H. for disease education and screening activities, and grant number NU2GGH to C. C. and grant number 5NU2GGH to M. E. for disease prevention and control activities); and Texas State University (to M. E. for screening of newborns for Chagas disease).
Potential conflicts of interests. C. B. reports royalty payments for topics related to Chagas disease epidemiology, diagnosis, and treatment. For C. B. the source of royalty payments is UpToDate, published by Wolters Kluwer Health. Y. E. and C. S. reports receiving test kit donations from InBios International, Inc. for use in research. M. E. and N. H. report honoraria for lectures related to Chagas disease. For M. E. sources of honoraria for lectures are Christus Health; Hollywood Presbyterian Hospital; Rhode Island Hospital; and Albert Einstein College of Medicine. For N. H. the source of honoraria is MetroWest Medical Center (for a Ground Rounds talk). All other authors report no potential conflicts. All authors have submitted the ICMJE Form for Disclosure of Potential Conflicts of Interest. Conflicts that the editors consider relevant to the content of the manuscript have been disclosed.
Presented in part: Second Rethinking Chagas Workshop, Harvard T. H. Chan School of Public Health, virtual, 19 May ; and IDWeek, virtual, 29 September'3 October .
Colin J Forsyth, Drugs for Neglected Diseases initiative, New York, New York, USA.
Jennifer Manne-Goehler, Division of Infectious Diseases, Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts, USA.
Caryn Bern, Department of Epidemiology and Biostatistics, University of California, San Francisco, San Francisco, California, USA.
Jeffrey Whitman, Department of Laboratory Medicine, University of California, San Francisco, San Francisco, California, USA.
Natasha S Hochberg, Department of Medicine, Section of Infectious Diseases, Boston University School of Medicine, Boston, Massachusetts, USA; Department of Epidemiology, Boston University School of Public Health, Boston, Massachusetts, USA; Boston Medical Center, Boston, Massachussetts, USA.
Morven Edwards, Department of Pediatrics, Baylor College of Medicine, Houston, Texas, USA.
If you want to learn more, please visit our website Chagas Rapid Test.
Rachel Marcus, Medstar Union Memorial Hospital, Washington, District of Columbia, USA; Latin American Society of Chagas, Washington, District of Columbia, USA.
Norman L Beatty, Division of Infectious Diseases and Global Medicine, University of Florida College of Medicine, Gainesville, Florida, USA.
Yagahira E Castro-Sesquen, Department of International Health, Johns Hopkins Bloomberg School of Public Health, Baltimore, Maryland, USA.
Christina Coyle, Division of Infectious Diseases, Albert Einstein College of Medicine and Jacobi Medical Center, Bronx, New York, USA.
Paula Stigler Granados, School of Public Health, San Diego State University, San Diego, California, USA.
Davidson Hamer, Department of Medicine, Section of Infectious Diseases, Boston University School of Medicine, Boston, Massachusetts, USA; Department of Global Health, Boston University School of Public Health, Boston, Massachusetts, USA.
James H Maguire, Division of Infectious Diseases, Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts, USA.
Robert H Gilman, Department of International Health, Johns Hopkins Bloomberg School of Public Health, Baltimore, Maryland, USA.
Sheba Meymandi, Center of Excellence for Chagas Disease, Olive View-University of California, Los Angeles Medical Center, Sylmar, California, USA.
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PMCID: PMC PMID:Chagas disease, caused by Trypanosoma cruzi, affects millions of people globally and is associated with significant underdiagnosis and undertreatment. Current diagnostic algorithms face challenges in remote regions. We aimed to review the potential of rapid diagnostic tests (RDTs) for screening or diagnosing chronic Chagas disease in endemic areas. An expert panel representing scientific and academic institutions from the Americas convened with the aim of discussing the use of RDTs. The study employed the nominal group technique, gathering insights from diverse experts during a 3-day meeting. Panel discussions covered RDT application, research protocols, and regulatory mechanisms. The results indicate that RDTs play a crucial role in surveillance and screening, although limitations in sensitivity and specificity exist. The expert group recommends standardized protocols, emphasizes the importance of cost-effectiveness assessments, and highlights the need to consider geographic validation. Despite these challenges, RDTs present a promising avenue for improving Chagas disease diagnosis in resource-limited settings. Future research and a collaborative approach are deemed essential for effective implementation.
Chagas disease, caused by the Trypanosoma cruzi parasite, affects approximately 7 million people globally, with potential cardiac or digestive complications in 30% of cases. Underdiagnosis and undertreatment in Latin America result from its often-silent progression, emphasizing the need for early and accurate diagnosis. A meeting of representatives from scientific and academic institutions discussed the use of rapid diagnostic tests (RDTs) for chronic Chagas disease covering RDT application, research protocols, and regulatory mechanisms, emphasizing the important role of this tool in rapidly detecting T. cruzi-specific antibodies. RDTs offer breakthroughs for remote areas. Currently recommended for screening, experts suggest evaluating their expanded use for definitive individual diagnosis, emphasizing their portability, minimal blood requirement, and rapid results. Challenges, including variability in RDT sensitivity and specificity, call for further research and evidence-based recommendations. The expert group highlights the need for standardized diagnostic protocols, reviewing regulatory aspects, and advocating for updates to diagnostic lists and improved supply management. In conclusion, the expert meeting provided a roadmap for optimizing RDTs in chronic Chagas disease diagnosis, balancing potential benefits with existing challenges. The proposed generic protocol aims to guide multicenter studies, positioning RDTs as valuable tools in addressing this public health issue across the Americas.
The World Health Organization (WHO) estimates that 7 million individuals worldwide are infected with Trypanosoma cruzi (T. cruzi), causing Chagas disease; with 30% at risk of cardiac or digestive pathologies [1,2]. Despite a high disease burden, predominantly in Latin America, less than 10% of T. cruzi carriers are diagnosed, and only 1% receive treatment [3]. The silent nature of the disease contributes to underdiagnosis; up to 70% of infected individuals may not develop any symptoms nor specific organ damage. Early, accurate diagnosis is crucial for effective treatment and the implementation of clinical management, control, and elimination measures.
In line with international recommendations from the Pan American Health Organization (PAHO) [4], the diagnosis of T. cruzi infection in the chronic phase of Chagas disease is made using serological tests. WHO and PAHO strongly recommend the use of at least 2 serological tests representing different methodological principles or antigens: one with high sensitivity (for instance, immunoenzymatic test referred to as the enzyme-linked immunosorbent assay) and one with high specificity (for instance, indirect hemagglutination) [4,5]. In cases of ambiguous or discordant results, a third serological technique should be used (for instance, indirect immunofluorescence) [6]. Despite its effectiveness, this algorithm requires time, laboratory infrastructure, and expertise often unavailable in many rural and hard-to-reach regions, resulting in the underdiagnosis and underreporting of infected individuals.
Latin America's complex health systems, which are set apart by the presence of diverse health subsystems, would benefit from the validation of suitable diagnostic tools for implementation in both highly complex facilities and primary care centers. Tools such as indirect chemiluminescence immunoassays (CLIAs), electrochemiluminescence immunoassays (ECLIAs), and chemiluminescence microparticle immunoassays (CMIAs) have been adopted by clinical laboratories at public healthcare facilities in major cities where fast, efficient, automated processing of a large number of samples is necessary [7]. In some Latin American countries, laboratories have independently begun implementing these tools to detect chronic T. cruzi infection, despite limited data on their diagnostic performance, using ad hoc algorithms depending on the jurisdiction involved. Before these techniques can be included in diagnostic algorithms recommended internationally by the PAHO, evidence obtained from diagnostic test evaluation studies should be analyzed to generate recommendations for the standardization of criteria and use.
In this context, improving access to diagnosis, especially in Chagas-endemic areas, is crucial. Currently, diagnostic laboratories are scarce and often inadequately equipped and/or staffed. Additional priorities include updating and enhancing diagnostic algorithms and methods, as well as gaining a better understanding of whether additional field studies are needed to establish the potential of point-of-care strategies for the diagnosis of chronic Chagas disease.
Over the past 2 decades, commercial development has yielded rapid diagnostic tests (RDTs) designed for detecting T. cruzi-specific immunoglobulin G (IgG) [8,9]. RDTs are easy-to-use point-of-care diagnostic tools that typically provide results within 30 minutes. These devices do not require electrical equipment, are storable, and are generally functional at room temperature. Additionally, some can work with very small samples of whole blood, enabling diagnosis by using finger pricks (peripheral blood samples). However, it is important to note that, at present, RDTs are recommended only for screening purposes and not for individual diagnosis. Serological confirmation of a patient is mandatory, potentially causing a delay in initiating treatment when recommended [1].
Recent studies suggest using RDTs with whole-blood samples to provide a quick, reliable, and definitive individual diagnosis of Chagas disease in remote areas [10,11]. A systematic review and meta-analysis showed that, worldwide, the sensitivity of the RDTs examined was good (greater than 95%), with excellent specificity (>99%), regardless of their use in endemic or nonendemic regions [12]. Nonetheless, the results of the overall published literature vary [13,14].
The objective of the present discussion was to review the existing evidence supporting the use of RDTs for screening or diagnosing chronic Chagas disease. Additionally, the aim was to discuss the implications of eventually adopting and implementing these tests as a strategy for diagnosing Chagas disease, considering their current reported accuracy and sustainability as a public health response in Latin America.
PAHO, in partnership with Fiocruz, through the CUIDA Chagas project (Communities United for Innovation, Development and Attention for Chagas Disease'Toward elimination of congenital transmission of Chagas disease in Latin America), convened a group of Chagas disease experts in Salvador, Bahia, Brazil, from September 7 to 9, . This meeting brought together a diverse panel of representatives from scientific and academic institutions from the Americas. Participation in the meeting was voluntary, and all the experts provided verbal informed consent for the use of the information provided.
The 3-day meeting facilitated discussions among more than 30 experts and participants from 9 countries (Argentina, Bolivia, Brazil, Chile, Colombia, Mexico, Uruguay, Switzerland, and the United States), addressing the objectives outlined earlier. The meeting agenda was structured around 3 main panels:
The use of RDTs for screening and diagnosis of chronic Chagas disease.
Existing research protocols for RDTs for Chagas disease.
Regulatory requirements and mechanisms for procuring RDTs for diagnosing Chagas disease in Latin American countries.
The nominal group technique, also known as the expert panel, was employed to gather firsthand information from relevant experts and determine the extent of their agreement on various topics [15]. Experts from the fields of clinical science, laboratory, parasitology, epidemiology, and research were purposefully sampled based on the diversity of their expertise and affiliations. Participation in the meeting was voluntary, and all the experts provided informed consent for the use of the information provided.
After each panel discussion, feedback was processed and summarized at key discussion points within the expert group. The meeting employed moderated plenary discussions. Deliberations took place in a total of 3 sessions of panel discussions in which the discussants offered their expert opinions. To complement the experts' discussion, 3 questions were formulated and debated in groups of 7 to 8 participants. Post meeting, the summary reports from each group were collated to generate a plenary report and summary recommendations, which were revised and approved by all participants.
RDTs have not been the sole diagnostic test for patients with chronic Chagas disease, with limited studies exploring this possibility [10,16]. According to the consensus among experts, RDT should not be employed in the diagnosis of acute cases of Chagas disease or in blood donors [5]. Current application of RDTs for chronic Chagas disease is restricted to specific situations, like epidemiological surveys or screening initiatives. The suggested systematic use of RDTs is proposed for special circumstances, emergencies and among at-risk populations residing in remote areas where small, low-capacity laboratories are prevalent or absent. Additionally, these tests can also be considered potential second diagnostic tools for case confirmation when no other recommended laboratory techniques are available, with an understanding of the limitations of this approach.
The expert group called attention to the fact that RDTs offer multiple options, but few quality studies have evaluated their performance. The literature consistently shows high specificity but insufficient sensitivity, with varying results depending on the test used [17]. More than 90% of RDTs exhibit specificity exceeding 95%. However, there is significant variability in sensitivity, a crucial factor in RDT usage. Consequently, their application is termed a 'diagnostic approximation' toward reaching a definitive diagnosis. However, further studies on this subject are imperative.
While RDTs are not utilized for treatment decisions, evidence suggests that they facilitate and potentially enhance access to diagnosis [18]. Due to their immediacy, a positive RDT result ensures prompt recruitment of patients with a suspected case for further study, confirmation, case management, potential referral, and/or treatment.
The group emphasized key advantages of RDTs, including portability, minimal blood sample and reagent volume, centrifugation-free processing, tolerance to temperature fluctuations (generally between 15 and 30 °C), and rapid results, facilitating swift and effective decision-making in specific situations. Additional advantages include ease of transport without refrigeration (except in higher temperature areas of Latin America) and applicability in non-laboratory settings.
Current RDTs detect specific antibodies using antigens selected by each manufacturer, necessitating evaluation by country-specific authorities. Notably, limited information exists about the trajectory, experience, and accumulated knowledge regarding the widespread use of RDTs in Chagas disease.
In general, RDTs exhibit excellent detection performance in patients with high antibody concentrations. However, challenges in effectiveness and performance may arise in Chagas disease cases with low antibody concentrations, representing 5% of the positive population, as presented in a study during the meeting [19]. Regarding RDT sample holders, experts stressed the critical need for permanent diagnostic test strips for subsequent verification and confirmation of readings, given that RDTs readings are operator dependent and that the strips may fade after a few minutes after use. The potential integration of smartphones-related methods to capture and document the output of test strips before they fade could be an option [20]. Additionally, practical constraints hinder simultaneous processing of large sample quantities, potentially resulting in delays in routine service delivery.
While some studies have assessed the performance of RDTs in Chagas disease [9], additional research is imperative to generate evidence that compares the effectiveness of available RDTs. Ideally, these studies should be conducted by research institutions and encompass diverse patient types and populations. Furthermore, there is currently insufficient evidence regarding the quality of RDTs for routine use, especially in primary care systems.
Comparative studies utilizing verified and accessible serum sample panels are essential for establishing standard procedural protocols. Strategies and criteria for the appropriate use of RDTs in various situations, including standard verification protocols, need to be developed, and evidence supporting their use must be established.
In conclusion, experts unanimously advocate that discussions on the future development of RDTs should be guided by the actual diagnostic needs of national health systems, patients, and users in general. The most effective RDTs will be those that align with real diagnostic needs or objectives set by providers of public health services.
From to , over 14 studies have explored various facets of Chagas disease diagnosis using RDTs [18]. These investigations covered diverse topics, including immunochromatography of sera from multiple origins, RDTs use in blood donors compared ELISA, and the field performance of RDTs in different demographic conditions, such as children, adolescents, and pregnant women, in both endemic and nonendemic regions. The studies also explored the use of RDTs among immigrants residing outside of Latin America and detected and compared the results from different RDTs [21].
Migration has brought the disease outside of the endemic countries, where the transmission continues vertically and via blood and tissue/organ donations. Recent studies have shown the pivotal role that RDTs for Chagas disease play in nonendemic regions [22]. Moreover, advancements in RDT technology have improved their sensitivity and specificity, enhancing their reliability in detecting Chagas disease even in low-prevalence settings [23]. By enabling early diagnosis and treatment, RDTs significantly contribute to public health efforts aimed at controlling the spread of this neglected tropical disease beyond its traditional endemic boundaries.
Experts concur a notable gap in cost-effectiveness and cost'outcome studies and that addressing those deficiencies is crucial for ensuring the accessibility and sustainability of RDTs. It is imperative to scrutinize related factors, including the regularity of production and supply. Moreover, various diagnostic technique combinations in studies suggest a sensitivity rate of 95%, encouraging exploration of different approaches like 'duo' RDTs, a single RDT combined with a single ELISA, or a single RDT combined with 2 ELISAs. To achieve this, rigorous studies with quality control measures are crucial, integrating protocols into generic frameworks.
Regarding specificity and sensitivity, experts urge consensus to establish universally accepted thresholds for RDT use in public health services. Systematic reviews with appropriate methodologies are needed to develop tables outlining the use of RDTs. These tables should summarize evidence derived from baseline pretest diagnostic probability, based on epidemiologic risk (high-risk, medium-risk, and low-risk populations). Additionally, there is a call for the development of new and improved studies to fortify the existing body of knowledge and facilitate evidence-based recommendations. It is proposed to create generic protocols, setting harmonized standards and procedures and quality control measures. For this, a critical step involves verifying RDT performance in diverse settings and among specific populations. Understanding the purpose and target populations for RDTs in Chagas disease patients is essential, and options for their use in specific scenarios, such as outbreaks or emergencies, should be explored, particularly for vulnerable groups such as children and women of childbearing age.
In the realm of RDTs for Chagas disease, the PAHO Strategic Fund stands as a vital technical cooperation mechanism for RDTs in Chagas disease, enhancing access and availability of diagnostic supplies [24]. Adhering to specific criteria, The Strategic Fund ensures the quality of the In Vitro Diagnostic (IVD) tests for member countries and employs tools to enhance demand planning and procurement processes.
A recommendation was made to update the list of IVD supplies for Chagas disease within the Strategic Fund. This update, supported by a group of experts, aims to facilitate access to validated diagnostic tests and expand the portfolio, providing countries with alternatives.
To assist countries in managing RDT supply, support includes identifying critical areas in the supply cycle, guiding demand planning, and implementing best practices for RDT kit procurement. Several barriers to the use of RDTs were identified, including health workers' lack of confidence in their accuracy, high costs, market sustainability challenges, and insufficient availability due to registration obstacles in the local health registries of some countries.
Regulatory challenges and obstacles include variations in clinical verification between countries, hindering health registration. Heterogeneous regulatory requirements, nonrecognition of international approvals, irregular production, market availability issues, and high costs also pose challenges in certain countries.
Opportunities for improvement in access to and availability of RDTs for the diagnosis of Chagas disease (identification of T. cruzi immunological response) have been identified. These opportunities include mapping acquisitions and estimating demand by country, describing the RDT market, conducting price studies in countries of the Region, and advocating for the harmonization of country regulations applicable to these diagnostic tests.
Based on published evidence or ongoing studies, is it possible to change current practices or international guidelines (such as those of PAHO) regarding the use of RDTs for screening and/or diagnosing chronic Chagas disease? What evidence is available for the use of combined RDTs as part of the diagnostic process (RDT-based diagnostic algorithms)? Is it possible to compare and use existing evidence generated by published or ongoing studies?
The consensus reached by experts emphasizes the current inadequacy of evidence to advocate for a shift in recommended practices concerning the use of RDTs in diagnosing individuals with Chagas disease. However, a strong recommendation emerges for the endorsement and backing of RDTs as valuable tools for surveillance and screening purposes. The continued use of these tools will increase the body of knowledge and evidence supporting the potential expansion of RDT usage in the future.
To enhance the quality and comparability of future studies, the expert group advised the development and adoption of standardized generic protocols. This approach is particularly crucial in the context of field studies, where comprehensive documentation of surrounding conditions, such as geographical area, bioecology, population type, and prevalence, is paramount. It is equally important to document the role of genetic variations of T. cruzi (described as Discrete Typing Units [DTUs]). Such a recording is expected to contribute substantially and robustly to the accumulation of knowledge on the subject.
Should RDTs be selected based solely on the sensitivity and specificity cutoff points indicated in the information published by the manufacturer? Or is it based on the performance of a certain brand over others? What other parameters or information, in addition to sensitivity and specificity, are essential for choosing an RDT for the diagnosis of chronic Chagas disease (considering endemicity and prevalence)?
The consensus reached throughout the group's discussion and plenary session concluded that the sensitivity and specificity reported by the manufacturer are insufficient for countries, public health systems and users to select a determined RDT. Verification of the sensitivity and specificity of RDTs is a critical responsibility that should rest with competent national authorities, including entities such as the national reference laboratory for public health. These authorities must ensure thorough documentation and reporting of the performance of RDTs within the country, disseminating this information through channels such as laboratory networks and end-users.
In addition to assessing sensitivity and specificity, it is crucial to document the positive predictive value of RDTs, evaluating their ease of use and practicality across diverse environments (urban versus rural, children versus adults). Furthermore, studies are necessary to examine the sustainability of the production and availability of existing RDTs. Additionally, conducting cost'benefit and cost-effectiveness studies is essential to provide a holistic understanding of their utility and impact.
Is preliminary geographic validation of RDT performance necessary before using RDTs in a particular geographic region, especially for diagnosing chronic Chagas disease?
The group unanimously confirmed the necessity of geographical validation of RDTs. The criteria for each country or subregion should be utilized for this purpose based on existing information regarding the similarity or diversity of bioecogeographic environments, genetic variations of the microorganism (DTUs), or the type of population to be screened. Emphasis was placed on the importance of distinguishing validation processes from verification processes. Manufacturers should conduct validation, including providing a comprehensive description of all RDT criteria and information.
On the other hand, verification should be performed by competent national authorities, such as the national reference laboratories of public health, using established protocols (for instance, Clinical and Laboratory Standards Institute (CLSI)). These protocols should require small sample sizes to evaluate RDT performance under more specific conditions, such as different batches of tests, ethnic groups, population types, or reactivity.
Various options for RDTs exist, but the current evidence regarding their performance in diagnosing Chagas disease is both heterogeneous and insufficient. RDTs, however, hold significant potential in public health, particularly in areas with limited access to health services, emergencies, screening, and field surveys. Despite their potential, technological and operational challenges persist, encompassing issues such as sensitivity, interpretation of results, test selection, availability, accessibility, and cost.
The development and implementation of simple, rapid tests and devices for point-of-care screening and treatment of neglected tropical diseases have significantly reduced morbidity and mortality in regions with limited access to laboratory services [25]. For instance, RDTs for malaria and dengue have made accurate diagnoses more available and feasible, thereby improving the quality of care [26'28].
Recognizing the pressing need to address diverse problems and diagnostic scenarios, which demand comprehensive approaches, PAHO has proposed formulating a generic protocol. This protocol will facilitate the development of multicenter national or regional studies that assess RDT performance, effectiveness, and costs. To support this initiative, a yet-to-be-established working group is recommended that is tasked with preparing a target product profile. This profile could guide the development and testing of RDTs, aiming to position them as screening tools and/or for complementary diagnosis of Chagas disease across different countries of the Region of the Americas.
We would like to thank the group of experts convened for attending and providing their insightful participation during the meeting activities. These are (in alphabetic order): Jaime Altcheh (Chagas and Parasitology Service, Hospital Gutiérrez'CABA, Argentina);Margarita Bisio (National Institute of Parasitology Mario Fatala Chaben, Argentina); Constança Britto (IOC/Fiocruz, Brasil); Laura Bohorquez (FIND, Colombia); Vania Cristina Canuto Santos (Pan American Health Organization, Brazil); Valentina Carranza (CUIDA Chagas, INI/Fiocruz, Brazil); Otacilio da Cruz Moreira (IOC/Fiocruz, Brazil); Eric Dumonteil (Tulane University); Andrea García (CUIDA Chagas, INLASA, Bolivia); Nora Giron (Pan American Health Organization, United States); Felipe Guhl (CIMPAT/UNIANDES); Carmen Guzman Bracho (Institute of Epidemiological Diagnosis and Reference, México); Claudia Herrera (Tulane University); María Isabel Jercic (Parasitology Department, Institute of Public Health, Chile); Constanza Lopez Albizu (National Institute of Parasitology Mario Fatala Chaben, Argentina); Alejandro Luquetti (Federal University of Goiânia, Brazil); Andrea Marchiol (Drugs for Neglected Diseases initiative (DNDi), Argentina); Arturo Munoz Calderon (INGEBI-CONICET, Argentina); Ana Pereiro (Mundo Sano Foundation, Argentina); María Jesús Pinazo (Drugs for Neglected Diseases initiative (DNDi)'Latin America, Bolivia); Juan Carlos Ramirez (Hospital de Niños Gutiérrez'CABA, Argentina); Ludovic Reveiz (Pan American Health Organization, United States); Alfonso Rosales (Pan American Health Organization, United States); Soledad Santini (Mario Fatala Chaben National Institute of Parasitology, Argentina); Franciana Maria Rosa de Silva (CUIDA Chagas, INI/Fiocruz, Brazil); Pablo Vega Rojas (UNITAID, Switzerland); Luiz Villarinho Pereira (CUIDA Chagas, INI/Fiocruz, Brazil).
The author is a staff member of the Pan American Health Organization. The author alone is responsible for the views expressed in this publication, and they do not necessarily represent the decisions or policies of the Pan American Health Organization.
Articles from PLOS Neglected Tropical Diseases are provided here courtesy of PLOS
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