ARCHITECT Chagas® as a single test candidate for Chagas disease diagnosis: evaluation of two algorithms implemented in a non-endemic setting

Objectives: To evaluate two algorithms for the diagnosis of chronic and congenital Chagas disease (CD), both including the chemiluminescent microparticle immunoassay ARCHITECT Chagas (R) (CMIA) as a single test but with an amended signal-to-cut-off ratio (S/CO) of >= 6, instead of an S/CO of >= 1 as indicated by the manufacturer. Methods: The study encompassed two panels of retrospective samples: 831 sera from 786 adolescents and adults (panel A), and 96 sera from 35 newborn infants with CD-infected mothers (panel B). A CMIA-negative result was deemed conclusive, whereas samples with an S/CO >= 0.8 were confirmed by a second test (BioELISA Chagas, ELISAr). Results: In panel A, seropositivity was 13% (102/786); 10 samples gave discordant results for CMIA and ELISAr, all of which were CMIA positive and had CD confirmed through a previous diagnosis by two positive serological tests. In panel B, all newborns were considered non-infected based on both a progressive decrease in antibody titres over time and negative real-time PCR results. CMIA still gave positive results in two infants aged 10 months but no S/CO values >6 were observed from 4 months on. Conclusions: CMIA is a firm candidate for use as a single CD diagnostic test in non-endemic countries. The algorithm with the >= 6 S/CO is as an efficient method for chronic CD diagnosis. CMIA could also be used as a single test to screen infants for congenital infection at the age of 10 months or even earlier if applying the corrected cut-off ratio, although further studies are required. (C) 2020 European Society of Clinical Microbiology and Infectious Diseases. Published by Elsevier Ltd. All rights reserved.