What is Flow Cytometry
Flow cytometry is a sophisticated laboratory technique that rapidly analyzes individual cells suspended in fluid as they pass single-file through a laser beam, measuring multiple physical and biochemical properties simultaneously through light scattering and fluorescence emission. 1
Core Technical Principles
The fundamental mechanism operates through three integrated systems:
Fluidic system: Cells suspended in liquid flow through a narrow channel at high velocity (meters per second), with hydrodynamic focusing positioning particles precisely in single file as they pass through the sensing region 2
Optical system: A laser beam interrogates each cell individually, generating light scatter patterns and fluorescence signals from fluorescent probe-labeled cells 1
Electronics system: Detectors capture forward scatter (cell size), side scatter (internal complexity/granularity), and fluorescence emissions from multiple fluorescent markers simultaneously 3, 4
The technique achieves analysis rates approaching 100,000 cells per second, enabling statistically robust assessment of both rare and common cell populations within minutes 2
Clinical Applications in Hematology
Flow cytometry serves as the gold standard for multiple critical diagnostic applications:
Acute leukemias and lymphoproliferative disorders: The International Myeloma Working Group recommends flow cytometry for diagnosis and monitoring, as it enables rapid, multiparametric analysis of cell populations 5
Plasma cell disorders: The European Hematology Association recommends it for differential diagnosis between neoplastic plasma cell disorders and reactive plasmacytosis through enumeration of plasma cells, demonstration of phenotypically abnormal and monoclonal cells, and assessment of multiple markers in combination with clonality 5
Lymphoma classification: The American Society of Hematology suggests flow cytometry facilitates classification through rapid determination of surface antigens on cells from lymph nodes and other masses 5
Key Advantages Over Alternative Methods
Multiparametric assessment: Flow cytometry provides more specific information through simultaneous evaluation of multiple markers than can be obtained by other diagnostic techniques such as immunohistochemistry 5
Quantitative precision: The technique allows volumetric sample delivery for accurate particle counting and enables reproducible enumeration that may be more reliable at predicting outcomes than morphological assessment 6
Speed and throughput: Analysis of thousands to millions of cells occurs within minutes, with high-throughput sampling technologies further increasing the rate at which independent samples can be processed 2
Cell Sorting Capability
Beyond analysis, flow cytometry can be coupled with sorting mechanisms to physically separate and collect specific cell populations based on their measured properties, enabling isolation of subpopulations for downstream applications 1, 3
Technical Considerations and Pitfalls
Sample quality: Discrepancies between flow cytometry and morphological assessment are primarily related to sample quality, with first-pull aspirate samples recommended for optimal results 6
Standardization requirements: Technical variations in flow cytometry methods can lead to inconsistent results, making standardization crucial for reproducible measurements 6