Flow-cytometric immunophenotyping is essential for the diagnosis and classification of various hematologic malignancies [1–6]. Flow cytometry also plays an important role in minimal residual disease (MRD) monitoring in acute leukemias and plasma cell neoplasms [7, 8]. To more accurately and sensitively detect malignant cells, flow cytometry technology has markedly advanced from three-to-four-color testing to multicolor testing, termed multiparametric flow cytometry. Recent advances in flow-cytometric testing are represented by next-generation flow cytometry, which enables highly sensitive MRD detection of up to a sensitivity of 1 in 10⁶ cells via an optimized combination of antibody reagents and high-throughput flow approaches [9]. However, the increasing complexity of flow-cytometric immunophenotyping, in terms of both the analysis and the composition of the panel of reagents, requires more expertise and personnel training. Depending on the expertise of researchers and laboratory technicians and the circumstances in the flow cytometry laboratory, high levels of subjectivity and variability can seriously affect the quality of the analysis. Therefore, there is an immense need to standardize flow-cytometric immunophenotyping for hematologic malignancies. There have been international attempts to standardize flow-cytometric immunophenotyping for the diagnosis and monitoring of hematologic malignancies, such as the EuroFlow projects [10]. The EuroFlow Consortium proposed a standardized flow cytometry approach encompassing instrument settings, antibody panels, sample preparation protocols, and data analysis protocols.

In the article by Park et al. [11] in this issue, survey data on flow-cytometric immunophenotyping from eight clinical laboratories at university hospitals in Korea have been published. The authors collected data on test items, reagent antibodies, fluorophores, sample amounts, reagent antibody amounts, acquisition cell numbers, isotype control usage, positive criteria, and reporting. According to the survey data, the number of reagent antibodies, fluorophores, sample amounts, reagent antibody amounts, and acquisition cell numbers varied between hospitals. Testing panels, positive criteria, and reporting had common characteristics across hospitals. Essential reagent antibodies are commonly tested in all hospitals, and optional antibodies may be tested based on the specific selection criteria of each hospital. As the authors pointed out, because the current standards for cell marker analysis for national health insurance coverage in Korea are 18 or less antibodies at initial diagnosis and five or less antibodies at follow-up, it is difficult for Korean hospitals to use larger numbers of antibody combinations, such as those used in the EuroFlow Consortium. This article also reveals that variability in the acquisition cell number and in the use of isotype controls instead of internal controls to determine positive results is common, which may affect achieving the sensitivity required for cell lineage determination and MRD monitoring.

As mentioned by Park et al., standardization of flow-cytometric immunophenotyping is an urgent and important task for the accurate and standardized diagnosis and monitoring of hematologic malignancies in Korea. Therefore, further efforts should be made by both the professional community and healthcare policymakers to adhere to international recommendations for current diagnostic and monitoring criteria for hematologic malignancies. The article by Park et al. in this issue of the Annals of Laboratory Medicine can be an important starting point.

Kim SY and Huh HJ both contributed to the writing of this manuscript and approved the submission of the final manuscript.

None declared.