Evaluation of a new <i>Trypanosoma cruzi</i> antibody assay for blood donor screening

Gorlin, Jed B.; Rossmann, Susan N.; Robertson, G. M.; Stallone, Fred; Hirschler, Nora V.; Nguyen, Kim-Anh; Gilcher, Ronald O.; Fernandes, Helen; Alvey, S; Ajongwen, Patience; Contestable, Paul; Warren, Harold

doi:10.1111/j.1537-2995.2007.01566.x

Cited by 43 publications

(29 citation statements)

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“…Apt68 did not bind to L. donovani promastigotes or the T. brucei blood stream forms and thus showed specificity only to T. cruzi trypomastigotes (Figure 4A, B). A major challenge for serological testing of Chagas disease is the high cross reactivity seen in patient sera with Leishmaniasis, African Trypanosomiasis and other parasitic diseases [23], [24]. This phenomenon has led to the high rates of false positivity seen in Chagas diagnostic assays [23], [24].…”

Section: Resultsmentioning

confidence: 99%

Development of an Aptamer-Based Concentration Method for the Detection of Trypanosoma cruzi in Blood

et al. 2012

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Trypanosoma cruzi, a blood-borne parasite, is the etiological agent of Chagas disease. T. cruzi trypomastigotes, the infectious life cycle stage, can be detected in blood of infected individuals using PCR-based methods. However, soon after a natural infection, or during the chronic phase of Chagas disease, the number of parasites in blood may be very low and thus difficult to detect by PCR. To facilitate PCR-based detection methods, a parasite concentration approach was explored. A whole cell SELEX strategy was utilized to develop serum stable RNA aptamers that bind to live T. cruzi trypomastigotes. These aptamers bound to the parasite with high affinities (8–25 nM range). The highest affinity aptamer, Apt68, also demonstrated high specificity as it did not interact with the insect stage epimastigotes of T. cruzi nor with other related trypanosomatid parasites, L. donovani and T. brucei, suggesting that the target of Apt68 was expressed only on T. cruzi trypomastigotes. Biotinylated Apt68, immobilized on a solid phase, was able to capture live parasites. These captured parasites were visible microscopically, as large motile aggregates, formed when the aptamer coated paramagnetic beads bound to the surface of the trypomastigotes. Additionally, Apt68 was also able to capture and aggregate trypomastigotes from several isolates of the two major genotypes of the parasite. Using a magnet, these parasite-bead aggregates could be purified from parasite-spiked whole blood samples, even at concentrations as low as 5 parasites in 15 ml of whole blood, as detected by a real-time PCR assay. Our results show that aptamers can be used as pathogen specific ligands to capture and facilitate PCR-based detection of T. cruzi in blood.

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Section: Resultsmentioning

confidence: 99%

Development of an Aptamer-Based Concentration Method for the Detection of Trypanosoma cruzi in Blood

et al. 2012

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“…Several reports had data from two or more tests simultaneously; therefore, there were 115 regular ELISA reports[22,25,43-105] (Additional file 1), 49 ELISA-rec reports [22,23,61,76,79,80,85,90,92,97,98,103,106-116] (Additional file 2) and 21 PCR reports[26,100,117-130] (Additional file 3), generating 185 tests results to analyze (figure 1). …”

Section: Resultsmentioning

confidence: 99%

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

et al. 2010

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BackgroundMost 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.MethodsA 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.ResultsHeterogeneity 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.ConclusionsBoth 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.

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“…In one study, only patients with a positive index test and a random selection of negative samples received the reference standard [19]. In other studies RIPA was only applied as part of the reference standard if the index or reference test was positive, while those initially negative either did not receive this test or only a random sample received the RIPA test [17], [20]. In another study, only samples positive by the index ELISA test were submitted to another ELISA test, and only those positive by both ELISA tests were submitted to a Western Blot.…”

Section: Discussionmentioning

confidence: 99%

A Systematic Review of High Quality Diagnostic Tests for Chagas Disease

2012

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BackgroundThere is significant heterogeneity in reported sensitivities and specificities of diagnostic serological assays for Chagas disease, as might be expected from studies that vary widely according to setting, research design, antigens employed, and reference standard. The purpose of this study is to summarize the reported accuracy of serological assays and to identify sources of heterogeneity including quality of research design. To avoid associated spectrum bias, our analysis was limited to cohort studies.MethodsWe completed a search of PubMed, a bibliographic review of potentially relevant articles, and a review of articles identified by a study author involved in this area of research. Studies were limited to prospective cohort studies of adults published since 1985. Measures of diagnostic accuracy were pooled using a Der Simonian Laird Random Effects Model. A subgroup analysis and meta regression were employed to identify sources of heterogeneity. The QUADAS tool was used to assess quality of included studies and Begg's funnel plot was used to assess publication bias.ResultsEighteen studies and 61 assays were included in the final analysis. Significant heterogeneity was found in all pre-determined subgroups. Overall sensitivity was 90% (95% CI: 89%–91%) and overall specificity was 98% (95% CI: 98%–98%).ConclusionSensitivity and specificity of serological assays for the diagnosis of Chagas disease appear less accurate than previously thought. Suggestions to improve the accuracy of reporting include the enrollment of patients in a prospective manner, double blinding, and providing an explicit method of addressing subjects that have an indeterminate diagnosis by either the reference standard or index test.

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Evaluation of a new Trypanosoma cruzi antibody assay for blood donor screening

Abstract: The ORTHO T. cruzi ELISA Test System is an effective, qualitative assay for screening blood donors for immunoglobulin G antibodies to T. cruzi. The assay was licensed for donor screening by the FDA in December 2006.

Cited by 43 publications

References 28 publications

Development of an Aptamer-Based Concentration Method for the Detection of Trypanosoma cruzi in Blood

Development of an Aptamer-Based Concentration Method for the Detection of Trypanosoma cruzi in Blood

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

A Systematic Review of High Quality Diagnostic Tests for Chagas Disease

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