Discrete clusters of ABL1-, and/or BIRC5-, and/or PRAME- and/or WT1-positive droplets were observed in active leukemia samples (Figure 2A). Of all patients tested, 61% (19/31) had evidence of active leukemia (MRD+ or overt relapse) at the time of ddPCR testing. This evidence concerns the gene ABL1 and leukemia.