VS38 Identifies Myeloma Cells With Dim CD38 Expression and Plasma Cells Following Daratumumab Therapy, Which Interferes With CD38 Detection for 4 to 6 Months.
OBJECTIVES
We report our institutional experience using VS38 to evaluate plasma cells by flow cytometry.


METHODS
Flow cytometry data were reanalyzed to compare plasma cell percentages between the standard panel and VS38 panel. Natural killer (NK) and plasma cell CD38 median fluorescence intensity (MFI) values were calculated.


RESULTS
Our cohort included 63 specimens from 38 patients. Twenty-six had received daratumumab (monoclonal anti-CD38 therapy) between less than 1 month and 17 months prior. For NK and plasma cells, CD38 MFI values were suppressed for 0 to 4 months and started to increase 4 to 6 months after last exposure. There was no significant difference in clonal plasma cell percentage calculated by the VS38 and standard panels; however, identification and quantification using the VS38 panel were easier.


CONCLUSIONS
VS38 is a viable alternative to bright CD38 to identify plasma cells and particularly helpful in myeloma cases with dim CD38 and after daratumumab. Daratumumab interference with CD38 identification persists 4 to 6 months after the last exposure.
['Courville|Elizabeth L|EL|', 'Yohe|Sophia|S|', 'Shivers|Paula|P|', 'Linden|Michael A|MA|']
D051997:ADP-ribosyl Cyclase 1 D000328:Adult D000368:Aged D000369:Aged, 80 and over D000911:Antibodies, Monoclonal D005260:Female D005434:Flow Cytometry D006801:Humans D007694:Killer Cells, Natural D008297:Male D008875:Middle Aged D009101:Multiple Myeloma D010950:Plasma Cells D013997:Time Factors
VS38 CD38 Plasma cells Daratumumab Flow cytometry Flow cytometric immunophenotyping Monoclonal antibody therapy Multiple myeloma Plasma cell myeloma Plasma cell neoplasm