PCR assay for monitoring Trypanosoma cruzi parasitemia in childhood after specific chemotherapy.

Assessment of cure of Trypanosoma cruzi infection by antibody seroconversion usually involves several years of follow-up. Parasitological negativity is useless for cure assessment, since even untreated patients mostly show negative results; conversely, positive tests are of great value because they indicate treatment failure. Here, PCR was used to assess the rate of specific chemotherapy failure in a well-characterized Brazilian cohort of T. cruzi-seropositive children, who were enrolled in a field trial of benznidazole (Bz) efficacy. Paired blood samples from 111 children were taken at baseline and 36 months after treatment with either Bz (n = 58) or a placebo (n = 53). DNA extraction and PCR amplification were carried out as previously described, and hybridization was performed with all PCR products. At the end of follow-up, PCR was positive for 39.6% of the patients in the Bz group versus 64.2% in the placebo group (P = 0.01). Untreated patients had a 1.6-fold-higher chance of remaining positive by PCR than those in the Bz group (P < 0.05). We conclude that PCR is a useful tool for revealing therapeutic failure of T. cruzi infection on a short-term basis.