title: Early mixed hematopoietic chimerism detection by digital droplet PCR in patients undergoing gender-mismatched hematopoietic stem cell transplantation.
abstract: BACKGROUND
  Clinical decision making after allogeneic stem cell transplantation (HSCT) is partially based on hematopoietic chimerism analysis. Polymerase chain reaction amplification of polymorphic short tandem repeats (STR-PCR) is currently considered the gold standard for chimerism surveillance after transplantation. Nevertheless, this method has shown several limitations. Emerging technologies such as digital PCR (dPCR) has been applied to detect hematopoietic chimerism. Despite previous reports, the clinical usefulness of dPCR is unclear because the studies were performed in limited patient populations with short follow-ups.
  
  
  METHODS
  In order to compare hematopoietic chimerism detection time and rate, we analyzed 591 samples from 155 patients undergoing gender-mismatched HSCT using STR-PCR and dPCR. We also established the correlation between both methods in artificial DNA mixtures prepared in known proportions and in clinical samples.
  
  
  RESULTS
  Depending on the artificial DNA mixture analyzed the correlation coefficient between both methods was 0.9946 and 0.9732. The limit of detection for dPCR was 0.01%. Of 157 samples with donor and recipient DNA, mixed chimerism (MC) was detected solely by dPCR in 66 samples. Within the group of patients relapsing after HSCT (n=32) MC was detected earlier in 15 of these patients with dPCR in comparison with STR-PCR. The mean time from MC detection to relapse was 155 days (range: 13-385 days) and 65 days (range: 0-203 days) for dPCR and STR-PCR, respectively.
  
  
  CONCLUSIONS
  dPCR is a sensitive and accurate method for the quantification of hematopoietic chimerism allowing earlier MC detection compared to STR-PCR.
authors.affiliation: .
authors.forename: Miguel
authors.initials: M
authors.lastname: Waterhouse
authors.affiliation: .
authors.forename: Dietmar
authors.initials: D
authors.lastname: Pfeifer
authors.affiliation: .
authors.forename: Marie
authors.initials: M
authors.lastname: Follo
authors.affiliation: .
authors.forename: Justus
authors.initials: J
authors.lastname: Duyster
authors.affiliation: .
authors.forename: Henning
authors.initials: H
authors.lastname: Schäfer
authors.affiliation: .
authors.forename: Hartmut
authors.initials: H
authors.lastname: Bertz
authors.affiliation: .
authors.forename: Jürgen
authors.initials: J
authors.lastname: Finke
mesh_terms: D000328:Adult; D000368:Aged; D005260:Female; D005500:Follow-Up Studies; D018380:Hematopoietic Stem Cell Transplantation; D006801:Humans; D008297:Male; D008875:Middle Aged; D016133:Polymerase Chain Reaction / Q000379:methods*; D018183:Transplantation Chimera / Q000235:genetics*; D055815:Young Adult
keywords: digital PCR; early detection; hematopoietic chimerism; hematopoietic stem cell transplantation