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

Abstract

Different approaches have been used in the di-agnosis of chronic Chagas disease. Serologic testsare used to detect antibodies against Trypanosomacruzi and not the presence of the parasite itself.These tests have high sensitivity but lack specific-ity because of antigenic cross-reactivity with para-sites such as Leishmania sp. and T. rangeli(Schmunis 1991, Saldana & Sousa 1996). Parasi-tological tests such as hemoculture or xenodiag-nosis have proven to be highly specific, but thesensitivity of these techniques is low. Recently,molecular assays such as the polymerase chain re-action (PCR), which amplify certain repetitive se-quences of trypanosome kinetoplast DNA (kDNA)have been proposed as a good alternative too fordetection 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 kinetoplastminicircles is normally used as a target for ampli-fication.The PCR assay has shown a variable degree ofefficiency. Initial sensitivity reports ranged from96% to 100% compared with serologic diagnosis(Avila et al. 1993, Wincker et al. 1994). A lowersensitivity level was observed by different research-ers (Britto et al. 1995b, Junqueira et al. 1996).These inconsistencies illustrate the need for addi-tional evaluation of large numbers of chagasic in-dividuals from different endemic regions in Brazildue to extensive variations in the incidence andclinical manifestations of Chagas disease in thiscountry.A new technique to verify cure in chagasic pa-tients who received specific treatment is needed.Conventional serologic tests such as the indirectimmunofluorescence (IIF) test, the indirect hemag-glutination test, and the ELISA are ineffective be-cause they are persistently positive in most treated