Performance of a novel eight‐color flow cytometry panel for measurable residual disease assessment of chronic lymphocytic leukemia

Abstract Background Measurable residual disease (MRD) is an important prognostic indicator of chronic lymphocytic leukemia (CLL). Different flow cytometric panels have been developed for the MRD assessment of CLL in Western countries; however, the application of these panels in China remains largely unexplored. Methods Owing to the requirements for high accuracy, reproducibility, and comparability of MRD assessment in China, we investigated the performance of a flow cytometric approach (CD45‐ROR1 panel) to assess MRD in patients with CLL. The European Research Initiative on CLL (ERIC) eight‐color panel was used as the “gold standard.” Results The sensitivity, specificity, and concordance rate of the CD45‐ROR1 panel in the MRD assessment of CLL were 100% (87/87), 88.5% (23/26), and 97.3% (110/113), respectively. Two of the three inconsistent samples were further verified using next‐generation sequencing. In addition, the MRD results obtained from the CD45‐ROR1 panel were positively associated with the ERIC eight‐color panel results for MRD assessment ( R = 0.98, p < 0.0001). MRD detection at low levels (≤1.0%) demonstrated a smaller difference between the two methods (bias, −0.11; 95% CI, −0.90 to 0.68) than that at high levels (>1%). In the reproducibility assessment, the bias was smaller at three data points (within 24, 48, and 72 h) in the CD45‐ROR1 panel than in the ERIC eight‐color panel. Moreover, MRD levels detected using the CD45‐ROR1 panel for the same samples from different laboratories showed a strong statistical correlation ( R = 0.99, p < 0.0001) with trivial interlaboratory variation (bias, 0.135; 95% CI, −0.439 to 0.709). In addition, the positivity rate of MRD in the bone marrow samples was higher than that in the peripheral blood samples. Conclusions Collectively, this study demonstrated that the CD45‐ROR1 panel is a reliable method for MRD assessment of CLL with high sensitivity, reproducibility, and reliability.