Acute promyelocytic leukemia (APL) is an aggressive disease that requires prompt treatment. Promyelocytic leukemia protein-retinoic acid receptor α (PML-RARα) fusion genes resulting from reciprocal translocation are considered a molecular basis for diagnosing APL. Moreover, PML-RARα fusion gene testing is an essential tool for monitoring the response to therapy via minimal residual disease and providing a diagnosis before rapid disease progression in APL. The present study developed a novel droplet digital PCR (ddPCR) assay to rapidly detect two PML-RARα variants (bcr1 and bcr3) and compared its limit of detection (LOD) with quantitative PCR (qPCR). It was demonstrated that the LOD of ddPCR for PML-RARα reached 0.001%, and the evaluation of high copy number samples of PML-RARα by ddPCR correlated well with qPCR. Furthermore, clinical sample testing with ddPCR found that 34 and 24% samples were bcr-1-positive and bcr3-positive, respectively. However, according to qPCR, 30% of the samples were bcr1-positive and 20% were bcr3-positive. In addition, the concordance rate between ddPCR and qPCR reaction was 86%. While monitoring minimal residual disease, the PML-RARα mutation rate of three patients who recovered well decreased to 0.34%. However, one patient who was bcr3-positive and relapsed had a mutation rate of 13% while in remission, indicating that the bcr3 isoform may be an adverse prognostic factor affecting recovery. Therefore, the present results suggested that this novel ddPCR assay may be useful for monitoring and evaluating the treatment effects and prognosis of APL.

急性早幼粒细胞白血病（APL）是一种侵袭性疾病，需要及时治疗。相互易位产生的早幼粒细胞白血病蛋白-视黄酸受体α（PML-RARα）融合基因被认为是诊断APL的分子基础。此外，PML-RARα融合基因测试是监测通过最小残留疾病监测治疗反应并在APL疾病快速发展之前提供诊断的重要工具。本研究开发了一种新颖的液滴数字PCR（ddPCR）分析法，可快速检测两个PML-RARα变体（bcr1和bcr3），并将其检测限（LOD）与定量PCR（qPCR）进行比较。证明了ddPCR对PML-RARα的检测限达到0.001％，并且ddPCR对PML-RARα高拷贝数样品的评估与qPCR密切相关。此外，使用ddPCR进行的临床样本测试发现34％和24％的样本分别为bcr-1阳性和bcr3阳性。但是，根据qPCR，样本中30％的bcr1阳性，而20％的bcr3阳性。另外，ddPCR与qPCR反应的一致性率为86％。在监测最小残留疾病的同时，PML-RARα恢复良好的三例患者的突变率降至0.34％。但是，一名bcr3阳性并复发的患者在缓解时突变率为13％，这表明bcr3亚型可能是影响恢复的不良预后因素。因此，目前的结果表明，这种新颖的ddPCR测定法可用于监测和评估APL的治疗效果和预后。