Chagas disease diagnosis using polymerase chain reaction, hemoculture and serologic methods.

Different approaches have been used in the diagnosis of chronic Chagas disease. Serologic tests are used to detect antibodies against Trypanosoma cruzi and not the presence of the parasite itself. These tests have high sensitivity but lack specificity because of antigenic cross-reactivity with parasites such as Leishmania sp. and T. rangeli (Schmunis 1991, Saldana & Sousa 1996). Parasitological tests such as hemoculture or xenodiagnosis have proven to be highly specific, but the sensitivity of these techniques is low. Recently, molecular assays such as the polymerase chain reaction (PCR), which amplify certain repetitive sequences of trypanosome kinetoplast DNA (kDNA) have been proposed as a good alternative too for detection of T. cruzi in human blood (Avila et al. 1993, Wincker et al. 1994, Britto et al. 1995a). The ≈330-base pair (bp) fragment of the kinetoplast minicircles is normally used as a target for amplification. The PCR assay has shown a variable degree of efficiency. Initial sensitivity reports ranged from 96% to 100% compared with serologic diagnosis (Avila et al. 1993, Wincker et al. 1994). A lower sensitivity level was observed by different researchers (Britto et al. 1995b, Junqueira et al. 1996). These inconsistencies illustrate the need for additional evaluation of large numbers of chagasic individuals from different endemic regions in Brazil due to extensive variations in the incidence and clinical manifestations of Chagas disease in this country. A new technique to verify cure in chagasic patients who received specific treatment is needed. Conventional serologic tests such as the indirect immunofluorescence (IIF) test, the indirect hemagglutination test, and the ELISA are ineffective because they are persistently positive in most treated