Antibody Detection
Infections with Trypanosoma cruzi are common in Central and South America.  Many immigrants from areas where Chagas disease is endemic currently reside in the United States and are potential sources for parasite transmission via contaminated blood.  During the acute stage of illness, blood film examination generally reveals the presence of trypomastigotes.  During the chronic stage of infection, parasites are rare or absent from the circulation; immunodiagnosis is a useful technique for determining whether the patient is infected.

The indirect fluorescent antibody (IFA) test is available at CDC.  IFA antigen slides are prepared from a suspension of epimastigotes.  Although IFA is very sensitive, cross-reactivity can occur with sera from patients with leishmaniasis, a protozoan disease that occurs in some of the same geographical areas as T. cruzi.  Various serologic methods are commercially available in the U.S. and other countries for laboratory diagnosis of Chagas disease.  The sensitivity and specificity of these tests are highly variable.

Positive IFA result with T. cruzi antigen (magnification 400×).