Applicability of a novel immunoassay based on surface plasmon resonance for the diagnosis of Chagas disease

Background: We defined the methodological criteria for the interpretation of the results provided by a novel immunoassay based on surface plasmon resonance (SPR) to detect antibodies anti-Trypanosoma cruzi in human sera (SPRCruzi). Then, we evaluated its applicability as a diagnostic tool for Chagas disease. Methods: To define the cut-off point and serum dilution factor, 57 samples were analyzed at SPRCruzi and the obtained values of SPR angle displacement (Delta theta(SPR)) were submitted to statistical analysis. Adopting the indicated criteria, its performance was evaluated into a wide panel of samples, being 99 Chagas disease patients, 30 non infected subjects and 42 with other parasitic/infectious diseases. In parallel, these samples were also analyzed by ELISA. Results: Our data demonstrated that 1:320 dilution and cut-off point at Delta theta(SPR) = 17.2 m degrees provided the best results. Global performance analysis demonstrated satisfactory sensitivity (100%), specificity (97.2%), positive predictive value (98%), negative predictive value (100%) and global accuracy (99.6%). ELISA and SPRCruzi showed almost perfect agreement, mainly between chagasic and non-infected individuals. However, the new immunoassay was better in discriminate Chagas disease from other diseases. Conclusion: This work demonstrated the applicability of SPRCruzi as a feasible, real time, label free, sensible and specific methodology for the diagnosis of Chagas disease. (C) 2015 Elsevier B.V. All rights reserved.