The aim of this study was to develop an internationally accepted plasmid certified reference material (CRM) that includes BCR–ABL1 and the three most commonly used CGs (ABL1, BCR and GUSB) to help calibrate all measurements of residual disease in CML, and in particular, levels of deep MR. This evidence concerns the gene BCR and chronic myelogenous leukemia, BCR-ABL1 positive.