title: Antibody levels correlate with detection of Trypanosoma cruzi DNA by sensitive polymerase chain reaction assays in seropositive blood donors and possible resolution of infection over time.
abstract: BACKGROUND
  The clinical significance of anti-Trypanosoma cruzi low-level reactive samples is incompletely understood. Polymerase chain reaction (PCR)-positive rates and antibody levels among seropositive blood donors in three countries are described.
  
  
  METHODS
  Follow-up samples were collected from T. cruzi-seropositive donors from 2008 through 2010 in the United States (n = 195) and Honduras (n = 58). Also 143 samples from Brazil in 1996 to 2002, originally positive by three serologic assays, were available and paired with contemporary follow-up samples from these donors. All samples were retested with Ortho enzyme-linked immunosorbent assay (ELISA). PCR assays were performed on coded sample panels by two laboratories (Blood Systems Research Institute [BSRI] and American Red Cross Holland Laboratory [ARC]) that amplified kinetoplast minicircle DNA sequences of T. cruzi.
  
  
  RESULTS
  PCR testing at BSRI yielded slightly higher overall sensitivity and specificity (33 and 98%) compared with those at the ARC (28 and 94%). Among seropositive donors, PCR-positive rates varied by country (p < 0.0001) for the BSRI laboratory: Brazil (57%), Honduras (32%), and the United States (14%). ELISA signal-to-cutoff ratios (S/CO) were significantly higher for PCR-positive compared to PCR-negative donors (p < 0.05 for all comparisons). Additionally, PCR-negative Brazilian donors exhibited greater frequencies of antibody decline over time versus PCR-positive donors (p = 0.003).
  
  
  CONCLUSIONS
  For all three countries, persistent DNA positivity correlated with higher ELISA S/CO values, suggesting that high-level seroreactivity reflects chronic parasitemia. Significant S/CO declines in 10% of the PCR-negative Brazilian donors may indicate seroreversion after parasite clearance in the absence of treatment.
authors.affiliation: Department of Infectious Disease, Institute of Tropical Medicine, University of São Paulo, São Paulo, Brazil.
authors.forename: Ester C
authors.initials: EC
authors.lastname: Sabino
authors.forename: Tzong-Hae
authors.initials: TH
authors.lastname: Lee
authors.forename: Lani
authors.initials: L
authors.lastname: Montalvo
authors.forename: Megan L
authors.initials: ML
authors.lastname: Nguyen
authors.forename: David A
authors.initials: DA
authors.lastname: Leiby
authors.forename: Danielle M
authors.initials: DM
authors.lastname: Carrick
authors.forename: Marcia M
authors.initials: MM
authors.lastname: Otani
authors.forename: Elizabeth
authors.initials: E
authors.lastname: Vinelli
authors.forename: David
authors.initials: D
authors.lastname: Wright
authors.forename: Susan L
authors.initials: SL
authors.lastname: Stramer
authors.forename: Michael
authors.initials: M
authors.lastname: Busch
mesh_terms: D000913:Antibodies, Protozoan / Q000097:blood*; D001782:Blood Donors / Q000706:statistics & numerical data*; D058731:Blood Safety / Q000706:statistics & numerical data*; D001938:Brazil / Q000453:epidemiology; D014355:Chagas Disease / Q000097:blood / Q000453:epidemiology / Q000276:immunology; D016054:DNA, Protozoan / Q000097:blood*; D004797:Enzyme-Linked Immunosorbent Assay / Q000379:methods; D005500:Follow-Up Studies; D006721:Honduras / Q000453:epidemiology; D006801:Humans; D016133:Polymerase Chain Reaction; D012680:Sensitivity and Specificity; D016036:Seroepidemiologic Studies; D014349:Trypanosoma cruzi / Q000235:genetics / Q000276:immunology / Q000302:isolation & purification*; D014481:United States / Q000453:epidemiology
chemical_list: D000913:Antibodies, Protozoan; D016054:DNA, Protozoan