Geographic Variations in Test Reactivity for the Serological Diagnosis of Trypanosoma cruzi Infection

Abstract

Chagas disease is a neglected disease caused by Trypanosoma cruzi parasites. Most of diagnosis is based on serological tests but the lack of a gold standard test complicates the measurement of test performance. To overcome this limitation, we used samples from a cohort of well-characterized T. cruzi infected women to evaluate the reactivity of two rapid diagnostic tests and one ELISA assay. Our cohort derived from a previous study on congenital transmission of T. cruzi , and consisted in 481 blood/plasma samples from Argentina (n=149), Honduras (n=228) and Mexico (n=104) with at least one positive T. cruzi PCR. Reactivity of the three tests ranged from 70.5% for the Wiener ELISA to 81.0% for the T-Detect and 90.4% for the Stat-Pak rapid tests. Test reactivity varied significantly among countries, and was highest in Argentina, and lowest in Mexico. When considering at least two reactive serological tests to confirm seropositivity, over 12% of T. cruzi infection cases from Argentina were missed by serological tests, over 21% in Honduras, and an alarming 72% in Mexico. Differences in test performance among countries were not due to differences in parasitemia, but differences in antibody levels against ELISA test antigens were observed. Geographic differences in T. cruzi parasite strains as well as genetic differences among human populations may both contribute to the discrepancies in serological testing. Improvements in serological diagnostics for T. cruzi infections are critically needed to ensure an optimum identification of cases.

Effect of clinician information sessions on diagnostic testing for Chagas disease

“…Here we only note that the large fraction of false positive obtained with the Hemagen ELISA placed a large burden on EBNHC staff who had to ensure confirmatory testing at the CDC. We do not know in what way our patients’ test results were affected by the significant variations in sensitivity of Chagas serologic testing recently noted in dependence on patients’ geographic region of origin [ 28 , 29 ]. Truyens and colleagues found that the sensitivity of the ELISA they examined varied between 89.7 and 27.9% [ 29 ].…”

Anaphylactic Reactions Due to Triatoma protracta (Hemiptera, Reduviidae, Triatominae) and Invasion into a Home in Northern California, USA

“…Despite sustaining "hundreds" of bites from triatomines over a 10-year period, frequently finding them inside his home, and evidence of T. cruzi-infected triatomines collected from inside the home, our patient did not have clinical or serological evidence of chronic CD. There has been some concern that certain T. cruzi DTU strains found within certain geographic regions in Mexico, as well as Central and South America, have discordant serological testing results [29][30][31][32]. The sensitivity and specificity of our available CD serological tests have not been assessed among those with autochthonous CD in the US at this time.…”

“…Our patient did have an HIV infection and was adherent to ART with sustained viral suppression and normal CD4 counts. Chagas disease among those with uncontrolled HIV/AIDS can lead to significant reactivation of T. cruzi and often times will be fatal [32,33]. Despite having CD4 counts greater than 200, T. cruzi DNA can still be detected in the blood of those infected with HIV, which likely indicates those living with HIV are at continued risk for reactivation Chagas disease [34].…”

Chagas Disease in Pregnant Women from Endemic Regions Attending the Hospital General de Mexico, Mexico City

“…The ABBOTT and Bio-Rad tests are commonly used serological tests for T. cruzi infection. Considering the variability by location of tests' performance [20][21][22], this in-house ELISA was chosen as a screening method because its antigens were grown using local parasite strains, as detailed below.…”

“…However, many of these tests are not readily available in most clinical settings [19]. Furthermore, many serological tests have been shown to perform differently in different geographic regions, in Mexico and across other Latin American countries [20][21][22].…”