Confirmation of subclonal SETBP1. (A) Mutant droplets were sorted, collected, and lysed for DNA. A Sanger tracing of sorted mutant droplet DNA from diagnosis revealed the SETBP1 c.2608G>A (p.D868N) mutation. (B) ddPCR at diagnosis using pooled bone marrow–derived DNA from the same patient showed a subclonal mutation at diagnosis not detected by Sanger sequencing. FAM (blue) droplets indicate the presence of mutant SETBP1 DNA; HEX (green) droplets indicate the presence of wild-type DNA; orange droplets indicate the presence of both mutant and wild-type DNA. (C) At relapse, a clonal SETBP1 mutation is clearly visible on ddPCR and Sanger sequencing. Percentages indicate the allelic fraction of mutant SETBP1.