title: Comparison between qualitative and real-time polymerase chain reaction to evaluate minimal residual disease in children with acute lymphoblastic leukemia.
abstract: BACKGROUND
  Minimal residual disease is an important independent prognostic factor that can identify poor responders among patients with acute lymphoblastic leukemia.
  
  
  OBJECTIVE
  The aim of this study was to analyze minimal residual disease using immunoglobulin (Ig) and T-cell receptor (TCR) gene rearrangements by conventional polymerase chain reaction followed by homo-heteroduplex analysis and to compare this with real-time polymerase chain reaction at the end of the induction period in children with acute lymphoblastic leukemia.
  
  
  METHODS
  Seventy-four patients diagnosed with acute lymphoblastic leukemia were enrolled. Minimal residual disease was evaluated by qualitative polymerase chain reaction in 57 and by both tests in 44. The Kaplan-Meier and multivariate Cox methods and the log-rank test were used for statistical analysis.
  
  
  RESULTS
  Nine patients (15.8%) were positive for minimal residual disease by qualitative polymerase chain reaction and 11 (25%) by real-time polymerase chain reaction considering a cut-off point of 1×10(-3) for precursor B-cell acute lymphoblastic leukemia and 1×10(-2) for T-cell acute lymphoblastic leukemia. Using the qualitative method, the 3.5-year leukemia-free survival was significantly higher in children negative for minimal residual disease compared to those with positive results (84.1%±5.6% versus 41.7%±17.3%, respectively; p-value=0.004). There was no significant association between leukemia-free survival and minimal residual disease by real-time polymerase chain reaction. Minimal residual disease by qualitative polymerase chain reaction was the only variable significantly correlated to leukemia-free survival.
  
  
  CONCLUSIONS
  Given the difficulties in the implementation of minimal residual disease monitoring by real-time polymerase chain reaction in most treatment centers in Brazil, the qualitative polymerase chain reaction strategy may be a cost-effective alternative.
authors.affiliation: Universidade Federal de Minas Gerais (UFMG), Belo Horizonte, MG, Brazil.
authors.forename: Francisco Danilo Ferreira
authors.initials: FD
authors.lastname: Paula
authors.affiliation: Universidade Federal de Minas Gerais (UFMG), Belo Horizonte, MG, Brazil.
authors.forename: Silvana Maria
authors.initials: SM
authors.lastname: Elói-Santos
authors.affiliation: Universidade Federal de Minas Gerais (UFMG), Belo Horizonte, MG, Brazil.
authors.forename: Sandra Guerra
authors.initials: SG
authors.lastname: Xavier
authors.affiliation: Centro Infantil Boldrini, Campinas, SP, Brazil.
authors.forename: Mônica Aparecida
authors.initials: MA
authors.lastname: Ganazza
authors.affiliation: Centro Infantil Boldrini, Campinas, SP, Brazil.
authors.forename: Patricia Yoshioka
authors.initials: PY
authors.lastname: Jotta
authors.affiliation: Centro Infantil Boldrini, Campinas, SP, Brazil; Universidade Estadual de Campinas (UNICAMP), Campinas, SP, Brazil.
authors.forename: José Andrés
authors.initials: JA
authors.lastname: Yunes
authors.affiliation: Universidade Federal de Minas Gerais (UFMG), Belo Horizonte, MG, Brazil.
authors.forename: Marcos Borato
authors.initials: MB
authors.lastname: Viana
authors.affiliation: Universidade Federal de Minas Gerais (UFMG), Belo Horizonte, MG, Brazil. Electronic address: julianaassumpcao@yahoo.com.br.
authors.forename: Juliana Godoy
authors.initials: JG
authors.lastname: Assumpção
keywords: Acute lymphoblastic leukemia; Leukemia free survival; Minimal residual disease; Polymerase chain reaction