Utility of Nine-Color, 11-Parameter Flow Cytometry for Detection of Plasma Cell Neoplasms

Abstract

Multiparameter flow cytometry (MFC) is a widely available laboratory platform for the evaluation of plasma cell (PC) neoplasms. We assess the performance of a nine-color MFC assay that uses stain-lyse-fix processing of bone marrow aspirates, minimal wash steps, and high acquisition rates with analysis of up to 1.8 × 10⁶ cells. MFC results were compared with microscopic examinations, immunohistochemical studies, and serum/urine M-protein measurements from patients with documented or suspected PC neoplasms. Sensitivity exceeded that of microscopic examinations, with or without immunohistochemistry. In patients with PC myeloma, clonal PC detection by MFC fell in concert with M-protein levels. However, in a subset of patients, MFC detected clonal PCs after serum/urine studies turned negative. The nine-color analytic cocktail eliminates duplication of PC gating reagents required for evaluation of the same epitopes using a five- or six-color approach. Fewer analytic cocktails result in lower instrument acquisition times per case, a significant factor for the large data sets required for optimal residual disease assessment. Finally, concurrent analysis of nine epitopes and two light scatter parameters aids detection of residual disease, particularly when it is mixed with polyclonal PCs.