Polymerase chain reaction (PCR) as a laboratory tool for the evaluation ofthe parasitological cure in Chagas disease after specific treatment

The evaluation of the treatment for chronic Chagas disease faces the absenc e of any clear-cut criterion of cure. The low degree of parasitemia and the persistence of positive immunologic reactions represent some of the diffic ulties involved in addressing therapeutic efficacy. Our aim was to define w hether PCR could be used as a laboratory method for evaluating cure in Chag as disease after specific treatment. We tested the utility of PCR amplifica tion of the variable regions of minicircles from Trypanosoma cruzi kinetopl ast DNA, in 76 xenopositive chronic Brazilian patients who have been treate d with benznidazole in Mambai (Goias State) and Sao Felipe (Bahia State). W e observed a positive amplification result in only 25 out of 76 treated pat ients (33%), Therefore, the performance of one single PCR after therapy rev ealed parasite clearance in 67% of the treated individuals, while xenodiagn osis was negative in 84%. These observations suggest that PCR is the most s ensitive technique available for direct detection of T. cruzi in chagasic p atients and that it can be a very useful instrument for the follow-up of pa tients after specific chemotherapy. In this sense, we are now developing a quantitative approach based on the use of fluorogenic probes and real-time measurement of the amplification reaction (TaqMan technology) in order to p recisely estimate the parasite load in chronic chagasic patients before and after treatment. This may be the basis for the future establishment of rel iable criteria of cure for patients undergoing therapy.