High ratio values on the IS scale, house-keeping control gene problems, variations in samples, delays in the exact molecular assessment time after TKI administration, and early unexpected variation kinetics of response in indivi dual CML patients complicate the universal application of the 10% BCR-ABL transcript cut-off at the 3rd month of TKI. This evidence concerns the gene ABL1 and chronic myelogenous leukemia, BCR-ABL1 positive.