The immunoglobulin M-Shed acute phase antigen (SAPA)-test for the early diagnosis of congenital Chagas disease in the time of the elimination goal of mother-to-child transmission

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Castro-Sesquen Y.E.
Tinajeros F.
Bern C.
Galdos-Cardenas G.
Malaga E.S.
Valencia Ayala E.
Hjerrild K.
Clipman S.J.
Lescano A.G.
Bayangos T.
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Oxford University Press
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Background: Diagnosis of congenital Chagas disease (CChD) in most endemic areas is based on low-sensitive microscopy at birth and 9-month immunoglobulin G (IgG), which has poor adherence. We aim to evaluate the accuracy of the Immunoglobulin M (IgM)-Shed Acute Phase Antigen (SAPA) test in the diagnosis of CChD at birth. Methods: Two cohort studies (training and validation cohorts) were conducted in 3 hospitals in the department of Santa Cruz, Bolivia. Pregnant women were screened for Chagas disease, and all infants born to seropositive mothers were followed for up to 9 months to diagnose CChD. A composite reference standard was used to determine congenital infection and was based on the parallel use of microscopy, quantitative polymerase chain reaction (qPCR), and IgM-trypomastigote excreted-secreted antigen (TESA) blot at birth and/or 1 month, and/or the detection of anti-Trypanosoma cruzi IgG at 6 or 9 months. The diagnostic accuracy of the IgM-SAPA test was calculated at birth against the composite reference standard. Results: Adherence to the 6- or 9-month follow-up ranged from 25.3% to 59.7%. Most cases of CChD (training and validation cohort: 76.5% and 83.7%, respectively) were detected during the first month of life using the combination of microscopy, qPCR, and/or IgM-TESA blot. Results from the validation cohort showed that when only 1 infant sample obtained at birth was evaluated, the qPCR and the IgM-SAPA test have similar accuracy (sensitivity: range, 79.1%-97.1% and 76.7%-94.3%, respectively, and specificity: 99.5% and 92.6%, respectively). Conclusions: The IgM-SAPA test has the potential to be implemented as an early diagnostic tool in areas that currently rely only on microscopy. © 2020 The Author(s) 2020. Published by Oxford University Press for the Infectious Diseases Society of America. All rights reserved.
The work was supported by Fondo Nacional de Desarrollo Cientifico, Tecnologico y de Innovacion Tecnologica, FONDECYT, Peru (N084-2016) to Y. E. C.-S.; the National Institutes of Health (R01-AI87776 and D43-TW010074 to R. H. G. and D43 TW007393 to A. G. L.); and InBios International, Inc to R. H. G. through the Johns Hopkins Bloomberg School of Public Health.
Palabras clave
Trypanosoma cruzi, Congenital Chagas disease, Diagnostics, IgM antibodies, Shed acute-phase antigen