Clinical Flow Cytometric Testing in Chronic Lymphocytic Leukemia

Flow cytometry is the cornerstone for establishing the diagnosis of chronic lymphocytic leukemia (CLL), owing to its characteristic and well-defined immunophenotype that enables accurate distinction from other leukemias and lymphomas. Beyond diagnosis, flow cytometry provides essential prognostic information and allows sensitive detection of minimal residual disease (MRD), a strong predictor of clinical outcome. CLL MRD assessment is increasingly used to guide risk stratification, therapeutic decision-making, and treatment duration in the era of targeted therapies and immunotherapies. This chapter reviews best practices for specimen collection, processing, staining, and data analysis and summarizes the principles of flow cytometric MRD assessment in CLL.