Use of the polymerase chain reaction (PCR) for the therapeutic control of chronic Trypanosoma cruzi infection

Abstract

Current norms for the etiological treatment of chronic Chagas disease, recommended by WHOor currently in force for Argentina and Brazil, advise the control of therapeutic efficacy usingconventional serological and parasitological tests. However, serology usually remains positive 10 ormore years after treatment and parasitological tests are insensitive in the chronic stage. PolymeraseChain Reaction (PCR) is more sensitive than parasitological tests and could provide earlier evidenceof therapeutic failure. We offered benznidazole treatment (5 mg/kg/day, 60 days) to 138 patients(age=16 to 35 years old), chronically infected with Trypanosoma cruzi. Therapeutic efficacy waschecked with periodic PCR, haemoculture and conventional serology in two groups of patients: One(TG) accepting and complying with treatment and the other (NTG) rejecting it. Before benznidazoleadministration, PCR displayed a diagnostic sensitivity of 41.3% (57/138) and haemoculture 7.2%(10/138). Sixty months after treatment, TG displayed a cumulated PCR positivity of 28.1% (16/57)and NTG 54.1% (20/37; p=0.0166). Even though the sensitivity of PCR is limited, repeated negativeresults of a standardized method may reveal lower parasitaemia or probable cure, in 71.9% of treatedpatients, to be confirmed with serological follow up.