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

Abstract Objectives To evaluate two algorithms for the diagnosis of chronic and congenital Chagas disease (CD), both including the chemiluminescent microparticle immunoassay ARCHITECT Chagas ® (CMIA) as a single test but with an amended signal-to-cut-off ratio (S/CO) of ≥6, instead of a 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 newborns with CD-infected mothers (Panel B). A CMIA negative result was deemed conclusive, whereas samples with a S/CO ≥0.8 were confirmed by a second test (BioELISA Chagas, ELISAr). Results In panel A, seropositivity was (102/786) 13%; 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 titers 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 four 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.