Strategy for detection of FIP1L1-PDGFRA fusion transcripts in CEL patients with heterogeneous breakpoint patterns. An appropriate forward primer (Table 1) was used in conjunction with the common probe (PDGFRA-Pr1) and reverse primer (PDGFRA-R1) according to the identified breakpoint location. The number of patients analyzed with any given assay is shown, together with the respective size of the amplicon.