The role of CD44 in the assessment of minimal residual disease of multiple myeloma by flow cytometry

Although the guidelines recommended some biomarkers for detecting minimal residual disease (MRD) in multiple myeloma (MM) by multiparameter flow cytometry (MFC), there is still room for the exploration of the selection of biomarkers for this purpose. To seek a more effective combination of biomarkers to monitor MRD in MM. A comparison of the expression of each biomarker (CD19, etc.) by MFC in the bone marrow of the MM group (56 MM patients with MRD) in comparison with the biomarker expression in the control group (49 non-MM patients) was conducted, and an analysis of the abnormal expression of each biomarker was assessed in each patient by a semiquantitative assay. The CD44 expression and median fluorescence intensity in myeloma cells were significantly lower than that in the control group (P = 0.000), and CD44 may be an alternative myeloma-specific biomarker. Subsequently, we obtained the positive threshold for each biomarker (except for CD49d and CD184), and the median number 4 (2, 6) of abnormal biomarkers was significantly higher in the MM group than in the control group (0, 2) (P = 0.000). We defined greater than 2 abnormal biomarkers as the criterion for diagnosing MRD in MM, and the sensitivity of the novel biomarker combination (including CD44; 94.64% sensitivity) was enhanced from that of the previous biomarker combination (except for CD44; 83.93% sensitivity). CD44 can serve as an alternative myeloma-specific biomarker. The novel MFC biomarker combination can more effectively evaluate MRD in MM and could be considered for use in clinical practice.