Complementary molecular tests: diagnosis of megaesophagus with conventional nonreactive or inconclusive serology for Chagas disease

Abstract Background: The current laboratory diagnosis of chronic Chagas disease (CD) relies on two serological tests based on distinct principles (ELISA, HAI, or IFI), which may yield false-positive and false-negative results. Blood culture (BC) can also be used as a diagnostic method, but its sensitivity in the chronic phase is limited. To assist in the outcome of a possible diagnosis of CD in cases of adult patients in which serological methods have conflicting or inconclusive results, both conventional and quantitative molecular methods have been used, especially the polymerase chain reaction (PCR) technique. This study aimed to evaluate the performance of qualitative and quantitative molecular methods for diagnostic purposes in patients with megaesophagus and nonreactive or inconclusive conventional serology for CD.Methods: This was a prospective cohort study of 26 participants with negative or inconclusive conventional serology for CD and 33 participants with positive serology who were treated at a referral center from 2010–2011. Peripheral blood samples were collected intravenously at the same time for serological (ELISA and IFI), BC and molecular tests such as qualitative PCR, targeting the Sat-DNA and kDNA of T. cruzi and quantitative PCR (qPCR).Results: For the BC method, the results were negative in all cases in Group I and positive in five cases (21.73%) in Group II, with no statistically significant difference between the groups. For the molecular methods, positivity in relation to the kDNA target was 45.83% for Group I and 33.33% in Group II; for the Sat-DNA target, it was 76.29% in Group I and 63.63% in Group II, with a significant difference.Conclusion: Molecular tests can be used in nonreactive or inconclusive serological results and can be useful to confirm Chagas disease in cases of megaesophagus and nonreactive or inconclusive conventional serology for CD.