Use of a nested polymerase chain reaction (N-PCR) to detect Trypanosoma cruzi in blood samples from chronic chagasic patients and patients with doubtful serologies.

Chagas disease, caused by Trypanosoma cruzi, is an important endemic illness in Latin America. Serologic tests for T. cruzi detection in blood are sensitive, but their specificity is unsatisfactory. Direct detection of parasites in blood, either by xenodiagnosis or hemoculture, is highly specific but of low sensitivity. Molecular assays such as the Polymerase chain reaction (PCR), which amplifies certain repetitive sequences of nuclear DNA has been used as a good alternative tool for T. cruzi detection in human blood. The present study aimed to test PCR diagnosis in chagasic chronic patients and doubtful serologic patients attended in GEDOCH (Chagas Disease Study Group/UNICAMP, Brazil). A 149 bp fragment originated from nuclear DNA was specifically detected in chronic chagasic patients. The results of these tests were compared with serologic diagnosis performed using standard techniques and xenodiagnosis. We found that 43 out of 50 patients previously serodiagnosed as chagasic were positive using the N-PCR method. Thirteen of 30 patients with doubtful serologic results were confirmed as positive by N-PCR. Our results suggest that the N-PCR may be a complementary tool to serology in the diagnosis of Chagas disease, and that it is usefull for parasite detection in patients with chronic disease and patients with doubtful serologic results.