A century after its discovery, Chagas disease still represents a major neglected tropical threat. Accurate diagnostics tools as well as surrogate markers of parasitological response to treatment are research priorities in the field. The purpose of this study was to evaluate the performance of PCR methods in detection of Trypanosoma cruzi DNA by an external quality evaluation. An international collaborative study was launched by expert PCR laboratories from 16 countries. Currently used strategies were challenged against serial dilutions of purified DNA from stocks representing T. cruzi discrete typing units (DTU) I, IV and VI (set A), human blood spiked with parasite cells (set B) and Guanidine Hidrochloride-EDTA blood samples from 32 seropositive and 10 seronegative patients from Southern Cone countries (set C). Forty eight PCR tests were reported for set A and 44 for sets B and C; 28 targeted minicircle DNA (kDNA), 13 satellite DNA (Sat-DNA) and the remainder low copy number sequences. In set A, commercial master mixes and Sat-DNA Real Time PCR showed better specificity, but kDNA-PCR was more sensitive to detect DTU I DNA. In set B, commercial DNA extraction kits presented better specificity than solvent extraction protocols. Sat-DNA PCR tests had higher specificity, with sensitivities of 0.05–0.5 parasites/mL whereas specific kDNA tests detected 5.10⁻³ par/mL. Sixteen specific and coherent methods had a Good Performance in both sets A and B (10 fg/µl of DNA from all stocks, 5 par/mL spiked blood). The median values of sensitivities, specificities and accuracies obtained in testing the Set C samples with the 16 tests determined to be good performing by analyzing Sets A and B samples varied considerably. Out of them, four methods depicted the best performing parameters in all three sets of samples, detecting at least 10 fg/µl for each DNA stock, 0.5 par/mL and a sensitivity between 83.3–94.4%, specificity of 85–95%, accuracy of 86.8–89.5% and kappa index of 0.7–0.8 compared to consensus PCR reports of the 16 good performing tests and 63–69%, 100%, 71.4–76.2% and 0.4–0.5, respectively compared to serodiagnosis. Method LbD2 used solvent extraction followed by Sybr-Green based Real time PCR targeted to Sat-DNA; method LbD3 used solvent DNA extraction followed by conventional PCR targeted to Sat-DNA. The third method (LbF1) used glass fiber column based DNA extraction followed by TaqMan Real Time PCR targeted to Sat-DNA (cruzi 1/cruzi 2 and cruzi 3 TaqMan probe) and the fourth method (LbQ) used solvent DNA extraction followed by conventional hot-start PCR targeted to kDNA (primer pairs 121/122). These four methods were further evaluated at the coordinating laboratory in a subset of human blood samples, confirming the performance obtained by the participating laboratories. This study represents a first crucial step towards international validation of PCR procedures for detection of T. cruzi in human blood samples. A century after its discovery, Chagas disease, caused by the parasite Trypanosoma cruzi, still represents a major neglected tropical threat. Accurate diagnostics tools as well as surrogate markers of parasitological response to treatment are research priorities in the field. The polymerase chain reaction (PCR) has been proposed as a sensitive laboratory tool for detection of T. cruzi infection and monitoring of parasitological treatment outcome. However, high variation in accuracy and lack of international quality controls has precluded reliable applications in the clinical practice and comparisons of data among cohorts and geographical regions. In an effort towards harmonization of PCR strategies, 26 expert laboratories from 16 countries evaluated their current PCR procedures against sets of control samples, composed by serial dilutions of T.cruzi DNA from culture stocks belonging to different lineages, human blood spiked with parasite cells and blood samples from Chagas disease patients. A high variability in sensitivities and specificities was found among the 48 reported PCR tests. Out of them, four tests with best performance were selected and further evaluated. This study represents a crucial first step towards device of a standardized operative procedure for T. cruzi PCR.

This report describes a real-time PCR (Q-PCR) strategy to quantify Trypanosoma cruzi (T. cruzi) DNA in peripheral blood samples from Chagas disease patients targeted to conserved motifs within the repetitive satellite sequence. The Q-PCR has a detection limit of 0.1 and 0.01 parasites/mL, with a dynamic range of 10⁶ and 10⁷ for Silvio X10 cl1 (T. cruzi I) and Cl Brener stocks (T. cruzi IIe), respectively, an efficiency of 99%, and a coefficient of determination (R²) of 0.998. In order to express accurately the parasitic loads: (1) we adapted a commercial kit based on silica-membrane technology to enable efficient processing of Guanidine Hydrochloride-EDTA treated blood samples and minimize PCR inhibition; (2) results were normalized incorporating a linearized plasmid as an internal standard of the whole procedure; and (3) a correction factor according to the representativity of satellite sequences in each parasite lineage group was determined using a modified real-time PCR protocol (Lg-PCR). The Q-PCR strategy was applied (1) to estimate basal parasite loads in 43 pediatric Chagas disease patients, (2) to follow-up 38 of them receiving treatment with benznidazole, and (3) to monitor three chronic Chagas heart disease patients who underwent heart-transplantation and displayed events of clinical reactivation due to immunosupression. All together, the high analytical sensitivity of the Q-PCR strategy, the low levels of intra- and inter-assay variations, as well as the accuracy provided by the Lg-PCR based correction factor support this methodology as a key laboratory tool for monitoring clinical reactivation and etiological treatment outcome in Chagas disease patients. Infection with the parasite Trypanosoma cruzi (T. cruzi), causing American trypanosomiasis or Chagas disease, remains a major public health concern in 21 endemic countries of America, with an estimated prevalence of 8 million infected people. Chagas disease shows a variable clinical course, ranging from asymptomatic to chronic stages with low parasitaemias, whose severest form is heart disease. Diagnosis at the asymptomatic and chronic stages is based on serological detection of anti-T. cruzi antibodies, because conventional parasitological methods lack sensitivity. Current chemotherapies are more effective in recent infections than in the chronic adult population. The criterion of cure relies on serological conversion to negative, which may occur only years after treatment, requiring long-term follow-up. In this context, we aimed to develop a real-time PCR assay targeted to repetitive sequences of T. cruzi for sensitive quantitation of parasitic load in peripheral blood of infected patients. It was applied to monitor treatment response of infected children, allowing rapid evaluation of drug efficacy as well as detection of treatment failure. It was also used for early diagnosis of chagasic reactivation in end-stage heart disease patients who received immunosuppressive drugs after cardiac transplantation. This laboratory strategy may constitute a novel parasitological tool for prompt and sensitive evaluation of anti-parasitic treatment of Chagas disease.

The analytical validation of sensitive, accurate and standardized Real-Time PCR methods for Trypanosoma cruzi quantification is crucial to provide a reliable laboratory tool for diagnosis of recent infections as well as for monitoring treatment efficacy. We have standardized and validated a multiplex Real-Time quantitative PCR assay (qPCR) based on TaqMan technology, aiming to quantify T. cruzi satellite DNA as well as an internal amplification control (IAC) in a single-tube reaction. IAC amplification allows rule out false negative PCR results due to inhibitory substances or loss of DNA during sample processing. The assay has a limit of detection (LOD) of 0.70 parasite equivalents/mL and a limit of quantification (LOQ) of 1.53 parasite equivalents/mL starting from non-boiled Guanidine EDTA blood spiked with T. cruzi CL-Brener stock. The method was evaluated with blood samples collected from Chagas disease patients experiencing different clinical stages and epidemiological scenarios: 1- Sixteen Venezuelan patients from an outbreak of oral transmission, 2- Sixty three Bolivian patients suffering chronic Chagas disease, 3- Thirty four Argentinean cases with chronic Chagas disease, 4- Twenty seven newborns to seropositive mothers, 5- A seronegative receptor who got infected after transplantation with a cadaveric kidney explanted from an infected subject. The performing parameters of this assay encourage its application to early assessment of T. cruzi infection in cases in which serological methods are not informative, such as recent infections by oral contamination or congenital transmission or after transplantation with organs from seropositive donors, as well as for monitoring Chagas disease patients under etiological treatment. Chagas disease, caused by the parasite Trypanosoma cruzi, is endemic in several Latin American countries and still represents a major neglected tropical threat. It is transmitted to humans by blood-sucking triatomine bugs, congenital transmission, blood transfusion, organ transplantation and by consuming food and juice contaminated with the parasite. Tools for accurate diagnosis and surrogate markers of parasitological response to treatment remain key needs in the field. This study focused on the evaluation of a novel quantitative PCR assay for the diagnosis and follow-up of patients with Chagas disease, on the basis of international guidelines for analytical validation of molecular diagnostic methods. The method allows the simultaneous amplification of parasite satellite DNA sequence and a heterologous internal amplification control that permits rule out false negative results due to inhibitory substances or loss of DNA during sample processing. It was evaluated in peripheral blood samples from acute and chronic patients as well as in umbilical cord blood samples from newborns to seropositive mothers. The performing characteristics of this assay position it as a promising candidate for application to clinical trials and kit developments.

Objectives: This prospective study focused on the evaluation of anti-parasitic therapy in congenital Chagas’ disease, diagnosed and monitored by PCR and conventional diagnosis. Materials and methods: We studied 152 children born to seroreactive mothers, living in a non-endemic area. Fifty infants aged 0–6 months (GA) were diagnosed by microhaematocrit and PCR and 102 children aged 7 months to 17 years (GB) were diagnosed by serology and PCR. Forty treated patients were monitored for 2 or 3 years by PCR and conventional methods. A competitive-quantitative PCR was used to determine pre-therapy parasitic loads and follow their post-treatment evolution. Results: In GA, the sensitivities of the PCR and microhaematocrit were 100% and 82.4% and their specificities 97% and 100%, respectively. In GB, the sensitivity of the PCR was 73.8% with a specificity of 100%. Pre-therapy parasitic loads ranged from 12.5 to 125 000 and 12.5 to 125 parasite genomic equivalents/mL of blood in GA and GB, respectively. PCR turned negative in all treated pre-therapy PCR positive patients before or at the end of treatment, which was followed by their seronegativation in 10/10 GA, in 3/5 children initiating therapy at 7 months to 2 years of age but in 0/16 initiating therapy at an older age. Two out of the latter patients were occasionally PCR positive during post-treatment, suggesting no parasitological response. Out of nine pre-therapy PCR negative patients, four turned seronegative after treatment, suggesting that in undetermined patients, undetectable parasitic burdens may lead to better post-treatment prognosis. Conclusions: PCR was useful for sensitive diagnosis and therapy monitoring, allowing early detection of refractory cases.

Background. One hundred years after the discovery of Chagas disease, it remains a major neglected tropical disease. Chronic Chagas heart disease (cCh