ABL1 and chronic myelogenous leukemia, BCR-ABL1 positive: The current gold standard method for monitoring therapy responses in CML is based on RQ-PCR of the BCR-ABL1 transcripts to determine whether the patient achieves and remains in molecular remission (<0.1%) or if BCR-ABL1 positive cells still persist, i.e. minimal residual disease (MRD).