Clinical Applications of Flow Cytometry
Flow cytometry is a sophisticated diagnostic technique primarily used for the diagnosis and monitoring of hematological malignancies, including leukemias, lymphomas, and multiple myeloma, as well as for immunophenotyping cells to discriminate between normal and neoplastic populations. Flow cytometry enables rapid, multiparametric analysis of cell populations at the single-cell level, allowing for identification, characterization, and enumeration of abnormal cells even when present in small numbers. 1, 2
Primary Clinical Applications
Hematological Malignancies
- Flow cytometry is mandatory for diagnosis and monitoring of acute leukemias and chronic lymphoproliferative disorders 3
- Enables differential diagnosis between neoplastic plasma cell disorders and reactive plasmacytosis 3
- Facilitates classification of lymphomas through rapid determination of surface antigens on cells from lymph nodes and other masses 4
- Detects abnormal B-cell populations through kappa/lambda light chain ratio assessment (abnormal when >4.0 or <0.25) 4
Multiple Myeloma and Related Disorders
Primary diagnosis of myeloma and associated disorders through:
- Enumeration of plasma cells in bone marrow
- Demonstration that a proportion of cells are phenotypically abnormal and monoclonal
- Assessment of multiple markers in combination with clonality 3
Risk stratification:
- Identifies independent prognostic markers predicting risk of progression in MGUS and asymptomatic myeloma
- Based on relative proportions of abnormal and normal plasma cells 3
Treatment monitoring:
- Quantitative evaluation of minimal residual disease (MRD)
- Assessment of treatment efficacy and prediction of outcomes
- Determination of stringent complete remission as defined by the International Myeloma Working Group 3
Other Applications
- Detection of disease-specific cell populations in paroxysmal nocturnal hemoglobinuria 5
- Assessment of immunological parameters for cancer immunotherapies 1
- Evaluation of chimeric antigen receptor (CAR) expression on engineered effector cells 1
Technical Recommendations for Flow Cytometry
Cell Identification and Enumeration
- CD38, CD138, and CD45 should all be included in at least one tube for plasma cell identification and enumeration 3
- Primary gating should be based on CD38 vs. CD138 expression 3
- For detection of abnormal plasma cells, a minimal panel should include CD19 and CD56 3
- A preferred panel would also include CD20, CD117, CD28, and CD27 3
Common Pitfalls and Considerations
- Discrepancies between plasma cell percentages detected by flow cytometry and morphology are primarily related to sample quality 3
- Important to determine that marrow elements are present in follow-up samples, particularly normal plasma cells in MRD negative cases 3
- Hodgkin's disease cannot be reliably detected by flow cytometry as currently used, and approximately 15% of lymphomas may show normal results 4
- Loss of architectural relationships during specimen processing is a major disadvantage when small foci of lymphoma exist with large amounts of stroma or normal lymphocytes 4
Advantages Over Conventional Techniques
- Ability to acquire multiparametric data in a relatively shorter time 1
- Facilitates comparative analysis of specific cellular subsets efficiently 1
- Enables physical sorting of cells to separate subpopulations based on different parameters 2
- Provides more specific information through multiple marker assessment than can be obtained by other diagnostic techniques such as immunohistochemistry 3
Recent Advances
- Imaging flow cytometry, mass cytometry, and Raman flow cytometry are being developed to address limitations of traditional flow cytometry 2
- Integration with advanced genetic tests for personalized precision-based immunotherapy 1
- Incorporation of 8-10 antibodies in a single tube allows for more comprehensive analysis but may create more complex technical and interpretation issues 6