Droplet digital PCR for BCR / ABL (P210) detection of chronic myeloid leukemia: A high sensitive method of the minimal residual disease and disease progression

Objective This study intended to establish a droplet digital PCR (dd‐ PCR ) for monitoring minimal residual disease ( MRD ) in patients with BCR / ABL (P210)‐positive chronic myeloid leukemia ( CML ), thereby achieving deep‐level monitoring of tumor load and determining the efficacy for guided clinically individualized treatment. Methods Using dd‐ PCR and RT ‐ qPCR , two cell suspensions were obtained from K562 cells and normal peripheral blood mononuclear cells by gradient dilution and were measured at the cellular level. At peripheral blood ( PB ) level, 61 cases with CML ‐chronic phase ( CML ‐ CP ) were obtained after tyrosine kinase inhibitor (TKI) treatment and regular follow‐ups. By RT ‐ qPCR , BCR / ABL (P210) fusion gene was undetectable in PB after three successive analyses, which were performed once every 3 months. At the same time, dd‐ PCR was performed simultaneously with the last equal amount of cDNA . Ten CML patients with MR 4.5 were followed up by the two methods. Results At the cellular level, consistency of results of dd‐ PCR and RT ‐ qPCR reached R 2  ≥ 0.99, with conversion equation of Y  = 33.148 X 1.222 (Y: dd‐ PCR results; X: RT ‐ qPCR results). In the dd‐ PCR test, 11 of the 61 patients with CML (18.03%) tested positive and showed statistically significant difference ( P  < .01). In the follow‐up of 10 CML patients who were in MR 4.5. All patients were loss of MR 4.0, and 4 were tested positive by dd‐ PCR 3 months earlier than by RT ‐ qPCR . Conclusion In contrast with RT ‐ qPCR , dd‐ PCR is more sensitive, thus enabling accurate conversion of dd‐ PCR results into internationally standard RT ‐ qPCR results by conversion equation, to achieve a deeper molecular biology‐based stratification of BCR / ABL (P210) MRD . It has some reference value to monitor disease progression in clinic.