From the Guidelines
Flow cytometry of bone marrow provides critical information about cell populations, including the identification and quantification of hematopoietic stem cells, myeloid cells, lymphoid cells, and abnormal cell populations, which is essential for diagnosing and managing hematologic malignancies. The primary clinical applications of flow cytometry in bone marrow analysis include differential diagnosis of neoplastic plasma cell disorders from reactive plasmacytosis, identifying risk of progression in patients with monoclonal gammopathy of undetermined significance (MGUS), and detecting minimal residual disease 1. Key technical recommendations for flow cytometry in bone marrow analysis include the use of CD38, CD138, and CD45 for plasma cell identification and enumeration, with the primary gate based on CD38 vs. CD138 expression 1. For detection of abnormal plasma cells, a minimal panel should include CD19 and CD56, with a preferred panel also including CD20, CD117, CD28, and CD27 1. In the context of minimal residual disease (MRD) assessment, flow cytometry is a valuable tool, with studies demonstrating its strong correlation with risk for relapse and prognostic significance in patients with acute lymphoblastic leukemia (ALL) 1. The optimal sample for MRD assessment is the first pull or early pull of the bone marrow aspirate, and current flow cytometry methods can detect leukemic cells at a sensitivity threshold of at least 1x10⁻⁴ (<0.01%) bone marrow mononuclear cells (MNCs) 1. Therefore, flow cytometry is a crucial diagnostic and monitoring tool in the management of hematologic malignancies, providing detailed information about cell populations and enabling accurate diagnoses and treatment plans. Some of the key benefits of flow cytometry in bone marrow analysis include:
- Identification and quantification of different cell types
- Detection of abnormal expression patterns of cell surface and intracellular markers
- Determination of the lineage of malignant cells and assessment of their maturation stage
- Identification of specific genetic abnormalities through immunophenotyping
- Monitoring of minimal residual disease after treatment and evaluation of treatment response
- Detection of relapse before clinical symptoms appear 1.
From the Research
Information Provided by Flow Cytometry
Flow cytometry provides detailed information about the cell composition and maturation in the bone marrow, including:
- Cell surface antigen expression 2, 3
- Nucleic acid content 3
- Cell size and granularity 3, 4
- Identification of immature and mature cell clusters 2
- Quantitation of plasma cells 5
Cell Lineage and Maturation
Flow cytometry can identify maturational differences of erythroid lineage cells in normal human bone marrow, including:
- Expression of cell surface markers such as HLe-1, transferrin receptor, and glycophorin 3
- Changes in cellular nucleic acid content corresponding to different stages of erythroid development 3
Applications and Limitations
Flow cytometry has various applications in the analysis of bone marrow cells, including:
- Immunophenotyping of peripheral blood cells 4
- Analysis of apoptosis and detection of cytokines 4
- Quantitation of plasma cells 5 However, the accuracy of flow-based plasma cell quantitation compared to morphologic assessment is uncertain, and differences in sample quality and cellular processing may affect the results 5