title: Definition of a diagnostic routine in individuals with inconclusive serology for Chagas disease.
abstract: Despite the existence of highly sensitive tests, inconclusive serological results are frequent in chronic chagasic infection. This study aimed to define a diagnostic conduct for 30 individuals with inconclusive serology (G3) for chagasic infection assisted at the Outpatient Unit for Infectious and Parasitic Diseases of the Botucatu School of Medicine. Twenty-one individuals with negative serology (G1) and 33 with positive serology (G2) were also studied. Serological methods ELISA, HAI, IFI and immunoblotting TESA-cruzi were used for G1, G2 and G3, and parasitological methods xenodiagnosis, hemoculture and PCR-LIT were used for G2 and G3 individuals. ELISA, HAI and IFI were performed in 5 different blood samples in G2 and G3. TESA-cruzi was carried out only once in G1, G2 and G3 and, since it is the most sensitive, it was utilized as standard. In G3, positivity for ELISA reached 86% in the fifth blood sample; the ELISA+HAI+IFI combination showed a maximum of 44.8% in the second sample; and TESA-cruzi, 76% in one single sample. Xenodiagnosis positivity was 9.4%; hemoculture showed 15.2%; and PCR-LIT exhibited 22% positivity in G2. Nevertheless, in G3, positivity percentage was 3.4% for xenodiagnosis, 6.7% for PCR-LIT, and no positive result was found for hemoculture. In G3, PCR-LIT resolved one case which was still inconclusive according to serology tests. In order to define inconclusive diagnoses, the results suggest the combined use of ELISA+HAI+IFI in 2 blood samples, decreasing the occurrence of false positive/negative results. If results remain inconclusive, the performance of TESA-cruzi and PCR-LIT, if necessary, is recommended.
authors.affiliation: Department of Tropical Diseases and Imaging Diagnosis, Botucatu School of Medicine, Universidade Estadual Paulista, 18618-000 Botucatu, SP, Brazil. mariele@fmb.unesp.br
authors.forename: Mariele Cristina Modolo
authors.initials: MC
authors.lastname: Picka
authors.forename: Domingos Alves
authors.initials: DA
authors.lastname: Meira
authors.forename: Thaís Batista
authors.initials: TB
authors.lastname: de Carvalho
authors.forename: Eliana
authors.initials: E
authors.lastname: Peresi
authors.forename: Jussara
authors.initials: J
authors.lastname: Marcondes-Machado
mesh_terms: D000818:Animals; D016022:Case-Control Studies; D014355:Chagas Disease / Q000175:diagnosis*; D002908:Chronic Disease; D005260:Female; D006801:Humans; D008297:Male; D016133:Polymerase Chain Reaction; D012680:Sensitivity and Specificity; D012698:Serologic Tests; D014349:Trypanosoma cruzi / Q000235:genetics* / Q000276:immunology*; D020525:Xenodiagnosis