POLYMERASE CHAIN-REACTION DETECTION OF TRYPANOSOMA-CRUZI IN HUMAN BLOOD-SAMPLES AS A TOOL FOR DIAGNOSIS AND TREATMENT EVALUATION

Trypanosoma cruzi specific sequences were amplified by the polymerase chain reaction from total blood of human chagasic patients and normal individuals. A 330 bp fragment originating from kinetoplast DNA was sp ecifically detected in most chagasic individuals. We tested the sensit ivity and specificity of this method in normal and affected individual s attending the Evandro Chagas Hospital, Rio de Janeiro. The results o f these tests were compared with serological diagnosis performed using standard techniques, and in some cases with xenodiagnosis. We found t hat none of the serologically negative individuals gave any specific a mplification product, whereas 55 out of 61 patients previously serodia gnosed as chagasic were positive using the PCR method (sensitivity: 90 %). Xenodiagnosis, which is currently considered to be the most sensi tive parasitological technique for Chagas' disease diagnosis, detected only 12 out of 28 serologically positive patients (sensitivity: 43 %) . The usefulness of the PCR method was further investigated with chaga sic patients who had received anti-parasite treatment with benznidazol e. It has always been difficult to evaluate the incidence of cure in s uch cases by serology, since a humoral response against T. cruzi antig ens may remain for years even in the absence of the parasite. We obser ved a positive amplification result in only 9 out of 32 treated patien ts who remained reactive when tested using classical serology. These o bservations suggest that PCR is the most sensitive technique available for direct detection of T. cruzi in chagasic patients and that it can be a very useful instrument for the follow-up of patients after speci fic treatment.