Interlaboratory consensus on the immunophenotypic diagnosis of chronic lymphocytic leukemia: Recommendations for the preparation of cytometric study reports and the selection of panels of monoclonal antibodies

Introduction . Immunophenotyping is a key diagnostic method for chronic lymphocytic leukemia (CLL), the most common lymphoproliferative disorder (LPD) in middle-aged and elderly individuals. Given the high prevalence of CLL, there is a need to standardize approaches to its immunophenotypic diagnosis, including the development of standardized panels of monoclonal antibodies, recommendations for sample preparation, and the formulation of reports to improve diagnostic accuracy. Aim : to develop a unified laboratory report form and a standardized approach to using the necessary and sufficient combination of labeled monoclonal antibodies for the diagnosis of CLL. Main findings . An All-Russian working group was formed under the National Hematological Society (NHS) to discuss key issues in the laboratory diagnosis of CLL. The primary focus was on problems related to immunophenotyping. Consensus decisions were made regarding the creation of a unified laboratory report form and a standardized approach to using the necessary and sufficient combination of labeled monoclonal antibodies for the diagnosis of CLL. The monoclonal antibody panel should include antibodies detecting CD19, CD20, CD5, CD23, and surface immunoglobulin light chains (k and λ). To differentiate CLL from other B-LPDs, additional markers such as CD43, CD200, CD10, CD22, and CD38 are recommended. The report form should include, along with patient information and sample type, the following: a list of used monoclonal antibodies, the flow cytometer model, the count of leukocytes and lymphocytes, the immunophenotype of the identified tumor population with emphasis on aberrant markers, the absolute count of pathological clone cells, and the final immunophenotypic variant of CLL or B-LPD.