Accuracy of Bone Marrow Flow Cytometry Analysis in Patients With Plasma Cell Neoplasm in Thailand: A Single Institutional Study

In this study, we evaluated plasma cells in bone marrow using flow cytometry in parallel with aspirate smear, marrow biopsy with immunohistochemistry, and protein electrophoresis. Flow cytometry detected abnormal plasma cells with high sensitivity (91.1%), specificity (96.9%), and accuracy (94.8%). Our study confirmed the feasibility of flow cytometry in establishing diagnosis and follow-up of plasma cell neoplasm after treatment. Background: Plasma cell neoplasm is a common hematologic malignancy. Treatment with novel agents results in favorable outcomes. Reliable investigations are required to monitor the residual disease, especially after such effective treatments. Flow cytometric analysis is a speedy and accurate method to detect abnormal cells. The aim of this study was to determine diagnostic performance of flow cytometry in the detection of abnormal plasma cells in bone marrow specimens. Materials and Methods: We included bone marrow samples taken from patients suspected to harbor plasma cell neoplasm at the time of diagnosis or follow-up after treatment from 2013 to 2015. Flow cytometric analyses, using cluster of differentiation (CD) 19/CD20/CD27/CD38/CD45/CD56/CD117/CD138 and cytoplasmic k/lambda, were done and results compared with morphologic evaluation of marrow aspirate smear, histology, and immunohistochemistry of marrow biopsy and protein electrophoretic analyses. Results: A total of 154 specimens were included. Plasma cell neoplasm was detected in 56 samples (36.4%). Most abnormal plasma cells in this study were CD19-negative (CD19(-))/CD20(-)/CD27(-)/CD38(-)/CD45(-) (or weakly positive)/CD56(+)/CD117(+)/CD138(+). Light chain restriction was found only in 18 samples (32.1%). Sensitivity and specificity of flow cytometric analysis were 91.1% and 96.9%, respectively. For the follow-up cohort, sensitivity and specificity were 86.7% and 66.7%, respectively. Conclusion: Analysis of plasma cell neoplasm using flow cytometry has high sensitivity and specificity. As an adjunct to marrow histology and immunohistochemistry, flow cytometry can be used in diagnosis of plasma cell neoplasm and more importantly in monitoring the disease after treatment. We propose a limited panel of CD19/CD38/CD45/CD56/CD117/CD138 for detecting minimal residual disease in Thai patients.