[Utility of 8-colours multiparameter flow cytometry immunophenotyping of plasma cells for the management of monoclonal gammopathy].

Bone marrow flow cytometric analysis is a powerful and rapid tool for evaluating aberrant plasma cell. In this study, we have examined the utility of multiparameter flow cytometry (MFC) in 52 patients with multiple myeloma (MM) and in 45 patients with monoclonal gammopathy with unknown significance (MGUS) into routine evaluation for the management of patients with plasma cell-related disorders. The plasma cells (PC) were identified by their light scatter distribution and reactivity patterns to CD138, CD38, and CD45. The combination of these parameters was helpful for identifying distinct subpopulations of PCs. Moderate to bright expression of CD56, CD20, CD24, CD28, and CD117 was detected in 67%, 26%, 13%, 27%, and 57% of MM cases and in 58%, 20%, 11%, 43% and 44% of MGUS cases, respectively. In MGUS group, the median percentage abnormal PCs/total PCs was 88% with 37 patients out of 45 (82%) with ratio <95%. The median ratio of the MM group was 98.9% and a ratio ≥ 95% was observed in 37 samples out of 44 (84%). In conclusion, MFC immunophenotyping of PCs has obvious clinical relevance in differential diagnosis between MM and others monoclonal gammopathies, identification of high-risk MGUS and smouldering MM, and minimal residual disease monitoring of MM. Our results showed that this tool can be easily applied in haematology laboratories.