Laboratory diagnosis of Chagas' heart disease

Abstract

The laboratory diagnosis of Chagas' disease is a complex one. Factors relating to the host immune response and the antigenic variability of T. cruzi must be considered in the final interpretation of tests results. Parasitologic methods for detecting T. cruzi, immunologic methods for detecting T. cruzi antigens in different biological fluids and serologic tests for detection and quantification of different classes of immunoglobulins are well standardized and used in the diagnosis of the acute or chronic phase of the disease. Xenodiagnosis is the most common parasitologic test employed, although it detects only 50% of infections in the chronic phase. Indirect immunofluorescence for detecting IgG and IgM antibodies, hemagglutination and enzyme immunoassay are the serologic tests most frequently employed for diagnosis, to screen blood donors and for seroepidemiologic studies. An important caveat to be remembered is that serologic tests provide only a probable diagnosis, which depends on the prevalence of Chagas disease, as well as on the sensitivity and specificity of the test employed. The use of well defined specific antigens, obtained through recombinant methods or chromatography, opens an important field for the development of very specific tests, without significant loss of sensitivity.

High prevalence anti-Trypanosoma cruzi antibodies, among blood donors in the State of Puebla, a non-endemic area of Mexico

“…In the particular case of Chagas disease, no serologic "gold" standard exists, since detection of T. cruzi-specific antibodies depends on many factors. Nevertheless, IFA is the most commonly used serologic test for Chagas disease and, as result, is widely accepted as the gold standard (Ferreira & Moraes de Avila 1995). Recent reports show that in-house IFA and in-house ELISA were highly concordant (Oelemann et al 1998).…”

Chagas' heart disease

“…Serologic tests -The etiologic diagnosis is routinely performed with methods that detect circulating antibodies that bind to parasite antigens 57 . The most commonly used tests are based upon complement fixation, immunofluorescence, or ELISA assays, that, carefully standardized, achieve sensitivity and specificity rates higher than 90 percent.…”

Clinical aspects of the Chagas' heart disease

“…The diagnosis of chronic T. cruzi infection is routinely achieved with methods that detect circulating antibodies that bind to T. cruzi antigens [30]. The most commonly used tests are based upon complement fixation, immunofluorescence, or ELISA assays.…”