Comparison of a PCR test based on the histone H2A/SIRE genes with classical serological tests for the diagnosis of chronic Chagas disease in Colombian patients

Introduction. Diagnosis of Chagas disease in its latent and chronic phase is difficult because of the low parasitemia levels. Therefore, serological and molecular techniques are necessary to achieve an appropriate diagnosis. Objective. The polymerase chain reaction based on the amplification of the SIRE element inserted into H2A encoding genes was compared with classical serological tests for the diagnosis of Chagas disease in Colombian patients. Materials and methods. An agreement study was carried out by comparing the PCR with ELISA (enzyme linked immuno sorbent assay) and FAT (indirect immunofluorescence) tests. In addition, the PCR sensitivity and specificity were determined. A sample of 156 individuals was tested with the H2A PCR primers after a Chagas disease classification based on clinical, epidemiological and serological data associated with each patient. In addition, 97 out of 156 samples were also compared with the S35/S36 PCR primers. Results. Eighty-nine of 156 samples (57%) were positive by both FAT and ELISA and 84 (53.8%) presented the expected 234 bp amplification fragment. The sensitivity of the TcH2AF/R PCR was 88% (95% C.I.: 75%--95%) and its specificity 92.5% (95% C.I.: 87.7%--97.2%). The kappa index for concordance between serological tests and TcH2AF/R PCR was 0.8 (95% C.I.: 73%--86%), and between the TcH2AF/R and S35/S36 PCR primers was 0.9 (95% C.I.: 84%-96%). These indices indicated a good and almost perfect agreement, respectively. Conclusions. The TcH2AF/R PCR is a promising diagnostic tool for the detection of T. cruzi and is suggested as a tool complementary to the classical serological tests.