What is the role of polymerase chain reaction assays in the diagnosis of Chagas disease (American trypanosomiasis)?

Updated: Apr 26, 2019
  • Author: Louis V Kirchhoff, MD, MPH; Chief Editor: Pranatharthi Haran Chandrasekar, MBBS, MD  more...
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Answer

The use of PCR tests for detecting T cruzi has been studied extensively over the past 25 years, and dozens of articles have described this approach. [129, 130]

The use of many distinct primer pairs has been described; the accumulated evidence suggests that assays based on TCZ1/TCZ2 (nuclear repetitive sequence) [131] and S35/S35 (kDNA minicircle conserved region) [132] are the most sensitive.

Methodologies for the best PCR assays for T cruzi have been published, [133, 134] but no kits are available commercially.

Although PCR assays generally appear to yield better sensitivity rates than xenodiagnosis or hemoculture, they are not high enough to justify their use for primary or confirmatory testing of blood donors or in clinical settings. The variable sensitivity is likely due to the extremely low parasite burden in chronically infected persons, meaning that the small blood samples taken for DNA extraction may not contain even a single parasite.

Nonetheless, there are several settings in which PCR assays for detecting T cruzi can have important roles. The first of these is in chronically infected patients who have been treated with benznidazole or nifurtimox. In this instance, a positive PCR result indicates treatment failure, but, given the variable sensitivity, a negative result is not meaningful. Secondly, PCR assays for T cruzi can play a role in detecting acute Chagas disease, particularly congenital T cruzi infection, since their sensitivities have been shown to be greater than microscopic examination in several contexts. [135, 136, 137, 138] Finally, PCR assays are the method of choice for detecting T cruzi infection in insect vectors [139, 140] and in food suspected of being contaminated with parasites. [141]


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