FIRST STEPS IN THE CLINICAL EVALUATION OF A SIMPLIFIED TEST TO DETECT CONGENITAL CHAGAS DISEASE ON NEWBORNS

L. LAROCCA; STOLOWICS FG; ONETO A; MACALLINI G; SMITHIUS F; DIMA E; ABUOLARA M; ARANDA C; VOJNOV A; CARRILLO C

Congreso; 18th International Congress on Infectious Diseases & XVIII Congreso SADI; 2018

Congenital Chagas disease (CCh) is caused by the protozoan Trypanosoma cruzi that can be vertically transmitted from infected women to their babies during pregnancy or childbirth. At most 1200 babies/year are born with CCh in Argentina, however less than 25% of cases are detected, due to diagnosis limitations. We recently developed the ?AMI-test?, a Loop-mediated Isothermal Amplification (LAMP) test for CCh detection. This is a simple test, with high analytical sensitivity and specificity, adapted to newborn screening (NS).The aim of this work was assessing our AMI test to detect CCh in NS Guthrie card samples. AMI test was assayed on remanent samples of Guthrie cards from NS (Durand Hospital, CABA Argentina), that were also evaluated by parasitemia -the only method currently validated for newborns- and serological tests at ~10 months old (gold standard). Positive controls (parasite spiked blood seeded in Guthrie cards) and negative controls (negative blood seeded in cards) were included.Test Subjects: Babies born from sero-positive mothers. Control Group: Newborns from sero-negative mothers. Selection Criteria: all newborn whose Guthrie Card and serology results from her/him (at ~10 months of age) and from her/his mother were available.Exclusion Criteria: lack of at least one of mentioned selection criteria. During two years, 286 Guthrie Card samples were collected: 186 from Test subjects - 60 of those met? all inclusion criteria-, and 100 negative samples ?which presented 94 AMI negative results, 1 false positive and 5 undetermined results- . In the case of the 60 Test subjects, a single case was detected by parasitemia and 9 others were positive applying the correspondent serological tests. Otherwise, 17 Test Subjects resulted positive by the AMI test, including the 10 lately mentioned (positives by serology and parasitemia) and 7 more, which could be either false positives, real positives detected by a more sensitive technique, or a combination of both. While parasitemia showed very low sensitivity (11%), AMI test yielded 100% sensitivity and a negative predicted value of 100%.To date, AMI test applied on Guthrie Cards appears to be significantly more sensitive than parasitemia, and easily suitable for congenital Chagas disease in newborns.