Comparison of minimal residual disease (MRD) estimated by flow cytometry and by real-time quantitative PCR of Wilms tumor gene 1 (WT1) transcript expression in children with acute lymphoblastic leukemia

Minimal residual disease (MRD) in 56 children with acute lymphoblastic leukemia (ALL) was quantified simultaneously by flow cytometry and by RQ-PCR of WT1 transcripts. Six patients failed remission induction, all had detectable MRD by flow cytometry, and two had undetectable MRD by WT1 assay. Among 41 patients, who achieved remission and had overexpression of WT1 transcripts at diagnosis, the two techniques gave concordant MRD results in 26 and discordant MRD results in 15. Nine patients did not show overexpression of WT1 at diagnosis. Our results indicate that RQ-PCR measurements of WT1 may be of limited value for monitoring MRD in childhood ALL.