ABL1 and acute lymphoblastic leukemia: This study therefore set out to develop and evaluate patient-specific qPCR MRD assays for paediatric ALL cases with EBF1-PDGFRB, SSBP2-CSF1R, NUP214-ABL1 and other ABL1 gene fusions and to compare the MRD results obtained with those based on IKZF1-deletion and conventional Ig/TCR qPCR MRD measurements.