A Modified FLT3 PCR Assay Using a TapeStation Readout

Background: FLT3 mutation testing is a key ancillary molecular assay for diagnosing and managing patients with acute myeloid leukemia (AML), including assessing the utility of FLT3 inhibitors during induction chemotherapy. FLT3 PCR utilizing fluorescently labeled primers and capillary electrophoresis readout is the most used technique for the rapid detection of FLT3 internal tandem duplications (ITDs) (including very small ITDs) and tyrosine kinase domain (TKD) mutations. However, capillary electrophoresis (CE) is a relatively lengthy and technically demanding result readout mode that could potentially be replaced by faster alternatives. Methods: Here, we describe the validation of a modified FLT3 PCR assay that uses the Agilent 4200 TapeStation platform for result readouts. This platform generates quantifiable electropherograms and gel images in under two minutes and at a low cost. We validated its ability to detect FLT3-ITD and -TKD mutations using 22 and 18 previously tested patient samples, respectively. Results: The TapeStation 4200 instrument is 100% sensitive, specific, and highly reproducible for post-PCR fragment analysis in detecting FLT3-ITD (greater than 15 bp in size) and TKD mutations in AML patients. Its results are nearly 100% concordant with those obtained from our previously validated NGS and PAGE methods. However, the limitation of this readout mode is its inability to reliably detect FLT3-ITDs smaller than 15 bp in size. Conclusions: Given the widespread use of TapeStation instruments in molecular diagnostics laboratories as part of next-generation sequencing (NGS) workflows, this modified assay is well-suited as a companion test for rapid NGS platforms to detect larger FLT3-ITDs, which are NGS often miscalledor under-called by the NGS bioinformatics algorithms. However, it is not suitable for use as a standalone assay, as it is unable to reliably detect very short FLT3-ITDs.