ABL1 and chronic myelogenous leukemia, BCR-ABL1 positive: However, in a previous study of BCR-ABL1 ALL [7], we demonstrated that MRD analysis using conventional MRD markers based on immunoglobulin and T-cell receptor (Ig/TCR) rearrangements fails to detect or underestimates MRD compared to qPCR genomic tests detecting the BCR-ABL1 gene fusion itself in some CML-like patients.