Qualitative polymerase chain reaction versus quantitative polymerase chain reaction for the detection of minimal residual disease in children with acute lymphoblastic leukemia

In acute lymphoblastic leukemia (ALL), remission is classically defined as the reestablishment of normal hematopoiesis and the presence of less than 5% of the nucleated blast cell population found by conventional microscopy; this is used in older protocols to assess treatment response.Morphological analysis, although useful and applicable at any center, has proven to be of limited sensitivity, subjective and imprecise to study early response to treatment and this technique does not appear to be sufficient to identify patients at true risk of relapse who might benefit from the intensification of treatment. 1,2For this reason, cytomorphological analysis has been replaced by minimal residual disease (MRD) monitoring in several treatment protocols and new definitions of remission and relapse in childhood ALL have been proposed. 3he analysis of MRD has proved to be the strongest independent prognostic factor in all studies analyzing large series of patients with B-lineage and T-cell ALL, and specific molecular subgroups such as patients with the BCR-ABL fusion gene and ALL patients with MLL gene rearrangements.5][6][7][8][9] MRD monitoring can also guide treatment decisions in relapsed patients and those who are candidates for bone marrow transplantation. 4,5,10,11