Diagnosis of Chagas Disease

Diagnosis of Chagas disease is related to the phase of this protozoan infection. For acute phase, parasitological methods are preferred and for the chronic phase, serological ones. Parasitological methods comprise from the simplest wet smear, going through alternatives as concentration methods and tests that involve the multiplication of the parasite in media (hemoculture), triatomine insects (xenodiagnosis), or animals (inoculation of susceptible mammals), to more sophisticated molecular tests as polymerase chain reaction (PCR) and loop-mediated isothermal amplification (LAMP). All have indications, advantages, and disadvantages, as well as costs, all of which will be detailed in this chapter. Among serological tests, a vast repertoire has been also developed and standardized, from the simplest indirect hemagglutination to the sophisticated CMIA, including indirect immunofluorescence, ELISA, and rapid tests. As all are indirect tests, it is recommended to use at least two of them for a concluding laboratory result, in order to confirm or exclude the infection by Trypanosoma cruzi. Diagnosis may be used in different contexts as confirmation of the infection, exclusion of blood donors, epidemiological survey, congenital infection, or follow-up after specific treatment. In order to have a precise diagnosis, it is necessary to have commercial kits of proved performance and good laboratory practices, for which permanent training of laboratory personnel is mandatory. An external quality control will prove that these conditions have been fulfilled.