Disagreement between PCR and serological diagnosis of Trypanosoma cruzi infection in blood donors from a Colombian endemic region

Introduction: Chagas' disease is the leading cause of infectious myocarditis worldwide. This infection caused by Trypanosoma cruzi is usually life-long and asymptomatic; however, the third part of infected people can develop severe or even fatal cardiomyopathy. As the parasitemia in the chronic phase is both low-grade and intermittent, T. cruzi infection is principally detected by serology, although this method has sensitivity and specificity limitations. Objective: To determine the level of agreement between serologic and molecular tests in 658 voluntary blood donors from six provinces in the Colombian department of Santander. Materials and methods: We evaluated an array of diagnostic technologies by cross-section sampling performing a serological double diagnostic test for T. cruzi antibody detection (Chagas III ELISA (TM), BiosChile Group, and ARCHITECT Chagas CMIA (TM), Abbott), and DNA detection by polymerase chain reaction (PCR). We collected the demographic, clinical, and epidemiological information of participants. The sample size was calculated using Epidat (TM) and the statistical analysis was done with Stata 12.1 (TM). Results: PCR was six times more sensitive in detecting T cruzi infection than ELISA/CMIA with prevalence values of 1.8% (12/658) and 0.3% (2/658), respectively, and kappa=0.28 (95%CI: -0.03 - 0.59). In contrast, serology showed a sensitivity of 16.7% (95%CI: 2.09 - 48.4) and a specificity of 100% (95%CI: 99.4 - 100). All seropositive samples were found to be positive by PCR. Conclusions: The implementation of PCR as a complementary method for screening donors could reduce the probability of false negative and the consequent risk of transfusional-transmission of Chagas' disease, especially in endemic regions.