Laboratory diagnosis of Trypanosoma cruzi infection: a narrative review

Abstract

Trypanosoma cruzi infection, currently endemic in 21 countries, is a public health problem not only in the Americas but also in countries with Latin American migrants. However, it is estimated that two-thirds of people with Chagas disease currently live in urban areas and that only 10% of them are aware of it. This review summarizes the most important aspects of the diagnosis of human T. cruzi infection by describing the following aspects of clinical laboratory diagnosis: the most widely used tests available in Latin America and those expected to improve access to diagnosis of the affected population with their implementation; the advantages, disadvantages, and sensitivity of the tests in the different phases of infection; and their usefulness in the acute or chronic phases of infection and in the context of immunosuppression. In this way, we hope to contribute to broadening the knowledge about this prevalent infection in the Americas.

Keywords: Chagas disease; Trypanosoma cruzi; diagnostic reagent kits; immunological tests; molecular diagnostic techniques; neglected diseases; parasitological diagnosis.

Figure 1

Stages of Trypanosoma cruzi in mammals. Hematoxylin-eosin staining, observation at 400X. (A) Trypomastigote: This form is elongated, with the kinetoplast located posterior to the nucleus. It is found in the blood of mammals and is the infective form. This form does not divide and is characterized by its mobility. (B) Nest of amastigotes: This form is spherical or oval and is the replicative form inside mammalian cells (mainly in muscle and nerve cells). This picture has been previously published [Lopez-Albizu et al. (2022)].

Figure 2

Schematic representation of parasitemia and specific anti-T. cruzi antibodies (Ab titer) in blood of infected patients during the course of infection. Some diagnostic tests used in each period of infection are shown as examples. Parasitemia: Microscopic image when performing the microhematocrit test in which the parasite is not seen but is illustrative of a preparation, since the search for the parasite is performed by observation of its movement, IIF: microscopic image of a preparation with serum from an infected subject, IHA: columns A, B: “sheaths” are observed as a result of the presence of anti-T. cruzi antibodies in the serum tested; columns C, D: “beads” are observed as a result of the absence of anti-T. cruzi antibodies in the serum tested. ELISA: image of an ELISA plate, showing the wells with positive results in yellow and negative results without staining. This picture has been previously published [Lopez-Albizu et al. (2022)].

Figure 3

Nucleic acid amplification tests for diagnosis of T. cruzi infection. (A) Molecular targets used in DNA amplification reactions; (B, C) Visualization of laboratory results of real-time PCR and LAMP tests, respectively. SatDNA, nuclear satellite DNA sequences; kDNA, minicircle of kinetoplast DNA; T.c (+), detectable T. cruzi DNA amplification; T.c (–), not detectable T. cruzi DNA amplification; IC (+), detectable internal control amplification. This picture has been previously published [Lopez-Albizu et al. (2022)].

Figure 4

Antigen-antibody interactions in serological tests designed to detect anti-T. cruzi antibodies using different principles, (A) IHA, (B) IIF, (C) ELISA. Ag, antigen; Ab, antibody.

Figure 5

Different antigens used in the diagnostic serological tests designed to detect anti-T. cruzi antibodies. (A) Total extract (lysate) or purified antigens; (B) Recombinant antigens; (C) Synthetic peptides. Ag, antigen; AA, amino acid; HPLC, high performance liquid chromatography.