Utility of Plasma Cell Screening Tube Kit to Differentiate Neoplastic Plasma Cells from Reactive Plasma Cells

ABSTRACT

Flow cytometry is a powerful tool for analysis of hematologic malignancies, that provides rapid, quantitative, and multiparametric analysis of heterogeneous cell populations, but requires standardization because of complexities in panel design and interpretation. Here, we compared the Plasma Cell Screening Tube (PCST) kit (Cytognos, Spain) in conjunction with EuroFlow antibody panels for standardization of flow cytometry to a conventional method for diagnosis of plasma cell dyscrasias. Thirty-nine bone marrow samples and one peripheral blood sample from 40 patients were tested. Thirty-three patients were diagnosed with multiple myeloma (MM), and seven were in a reactive state. In PCST implementation, eight antibodies were used for staining, including anti-CD45-Pacific Blue, anti-CD19-PECy7, anti-CD138-OC515, anti-CD38-FITC, anti-CD56-PE, anti-β2-microglobulin-PerCPCy5.5, anti-kappa-APC, and anti-lambda-APC-C750. Plasma cells were initially identified using CD38 and CD138; thereafter, CD38+, CD138+ gated cells were analyzed for CD56, CD19, CD45, cytoplasmic kappa, cytoplasmic lambda, and β2-microglobulin. Conventional flow cytometry was performed with six monoclonal antibodies, including anti-CD56-FITC, anti-kappa-FITC, anti-CD19-PE, anti-lambda-PE, anti-CD138-PECy5, and anti-CD45-PECy7 (Beckman Coulter, USA). Monoclonal plasma cells with cytoplasmic light-chain restriction were detected in 30 of 33 (90.9%) MM cases by conventional methods, and 32 of 33 (97.0%) MM cases with the PCST method. No differences were noted between PCST and the conventional method in immunophenotyping and plasma cell percentages (P=0.323). Among plasma cells, levels (%) were significantly higher by the PCST approach than those in the conventional method (97.6% vs 95.8%, P=0.010). PCST exhibited better performance for plasma cell dyscrasias diagnosis, and could improve laboratory efficiency and quality.