title: Chronic Chagas disease: PCR-xenodiagnosis without previous microscopic observation is a useful tool to detect viable Trypanosoma cruzi.
abstract: We evaluate the elimination of the microscopic stage of conventional xenodiagnosis (XD) to optimize the parasitological diagnosis of Trypanosoma cruzi in chronic Chagas disease. To this purpose we applied under informed consent two XD cages to 150 Chilean chronic chagasic patients. The fecal samples (FS) of the triatomines at 30, 60 and 90 days post feeding were divided into two parts: in one a microscopic search for mobile trypomastigote and/or epimastigote forms was performed. In the other part, DNA extraction-purification for PCR directed to the conserved region of kDNA minicircles of trypanosomes (PCR-XD), without previous microscopic observation was done. An XD was considered positive when at least one mobile T. cruzi parasite in any one of three periods of incubation was observed, whereas PCR-XD was considered positive when the 330 bp band specific for T. cruzi was detected. 25 of 26 cases with positive conventional XD were PCR-XD positive (concordance 96.2%), whereas 85 of 124 cases with negative conventional XD were positive by PCR-XD (68.5%). Human chromosome 12 detected by Real-time PCR used as exogenous internal control of PCR-XD reaction allowed to discounting of PCR inhibition and false negative in 40 cases with negative PCR-XD.
  
  
  CONCLUSIONS
  PCR-XD performed without previous microscopic observation is a useful tool for detection of viable parasites with higher efficiency then conventional XD.
authors.affiliation: Laboratorio de Parasitología Básico-Clínico, Programa de Biología Celular y Molecular, Instituto de Ciencias Biomédicas, Chile, izulanta@med.uchile.cl.
authors.forename: Miguel
authors.initials: M
authors.lastname: Saavedra
authors.affiliation: Laboratorio de Parasitología Básico-Clínico, Programa de Biología Celular y Molecular, Instituto de Ciencias Biomédicas, Chile, izulanta@med.uchile.cl.
authors.forename: Inés
authors.initials: I
authors.lastname: Zulantay
authors.affiliation: Laboratorio de Parasitología Básico-Clínico, Programa de Biología Celular y Molecular, Instituto de Ciencias Biomédicas, Chile, izulanta@med.uchile.cl.
authors.forename: Werner
authors.initials: W
authors.lastname: Apt
authors.affiliation: Laboratorio de Parasitología Básico-Clínico, Programa de Biología Celular y Molecular, Instituto de Ciencias Biomédicas, Chile, izulanta@med.uchile.cl.
authors.forename: Gabriela
authors.initials: G
authors.lastname: Martínez
authors.affiliation: Laboratorio de Parasitología Básico-Clínico, Programa de Biología Celular y Molecular, Instituto de Ciencias Biomédicas, Chile, izulanta@med.uchile.cl.
authors.forename: Antonio
authors.initials: A
authors.lastname: Rojas
authors.affiliation: Escuela de Salud Pública, Facultad de Medicina, Universidad de Chile, Santiago, Chile.
authors.forename: Jorge
authors.initials: J
authors.lastname: Rodríguez
mesh_terms: D000293:Adolescent; D000328:Adult; D000818:Animals; D014355:Chagas Disease / Q000175:diagnosis* / Q000469:parasitology; D002677:Chile; D002908:Chronic Disease; D005243:Feces / Q000469:parasitology; D006801:Humans; D008875:Middle Aged; D016133:Polymerase Chain Reaction; D012680:Sensitivity and Specificity; D014224:Triatoma / Q000469:parasitology*; D014349:Trypanosoma cruzi / Q000302:isolation & purification*; D020525:Xenodiagnosis / Q000379:methods*; D055815:Young Adult