Rapid diagnosis of acute promyelocytic leukemia with the PML-RARA fusion gene using a combination of droplet-reverse transcription-polymerase chain reaction and instant-quality fluorescence in situ hybridization

Acute promyelocytic leukemia (APL) with the PML-RARA fusion gene can be effectively cured using molecular-targeted therapies, which require both detection and quantification of the PML-RARA fusion gene. Here, we developed a rapid assay for identifying and measuring the PML-RARA fusion gene in patients with APL using droplet-reverse transcription-polymerase chain reaction (droplet-RT-PCR) and instant quality-fluorescence in situ hybridization (IQ-FISH). RNA for droplet-RT-PCR and fixed-cell suspensions for IQ-FISH were prepared from five patients with APL and three controls. We evaluated the amplification efficiency and reaction time with droplet-RT-PCR and signal clarity and hybridization time with IQ-FISH. The reaction using droplet-RT-PCR was completed in 26 min. The PML-RARA fusion gene was detected in all samples from the five patients. IQ-FISH yielded clear signals after 1 h of hybridization. There were no significant differences in signal clarity or positive signal ratios between IQ-FISH and conventional FISH. Simultaneous droplet-RT-PCR and IQ-FISH, in addition to morphological examination of blood smears, can be used to diagnose patients as having APL within 4 h based on molecular/cytogenetic results. Rapid diagnosis can allow effective therapies to be started promptly.