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KMID : 1100820230130040349
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Laboratory Medicine Online
2023 Volume.13 No. 4 p.349 ~ p.355
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Establishing a Reference Interval for Flow Cytometry-Based NK Activity (FC-NKA) Assay in Healthy Korean Population
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Kang Hyun-Hye
Choi Ae-Ran
Ryu Ji-Hyeong
Oh Eun-Jee
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Abstract
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Background : Flow cytometry (FC)-based natural killer cell activity (NKA) assays are commonly used in clinical laboratories. As low or no NKA is indicative of hemophagocytic lymphohistiocytosis (HLH), the precise determination of NKA levels is essential. The study aims to establish a reference interval for FC-NKA in healthy Korean subjects and determine the optimal cutoff for diagnosing HLH.
Methods : In a single-center retrospective study, internal quality control data from a total of 143 healthy individuals were analyzed. The FC-NKA assessed NK cytotoxicity by culturing effector cells with carboxyfluorescein diacetate succinimidyl ester-labeled K562 cells at an effector-to-target ratio of 32:1 for 4 hours. We compared the assay results among subgroups stratified by age and sex, as well as between healthy controls and HLH patients.
Results : The FC-NKA results did not vary significantly depending on age and sex. The reference interval drawn from the 2.5?97.5 percentile of the population was 13.8?82.9%. The lower limits of FC-NKA for the 5th and 10th percentiles were found to be 17.9% and 26.8%, respectively. Using receiver operating characteristic analysis, an optimal cutoff value of 20.0% was identified for HLH diagnosis with a sensitivity and specificity of 93.8% and 93.0%, respectively. The intra-individual coefficient of variation was determined to be 13.4% for the analysis of sequential samples from a single blood donor (N=8).
Conclusions : The reference interval of the FC-NKA was determined for healthy Korean subjects, and the suggested cutoff level has the potential to be utilized for the diagnosis of HLH.
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KEYWORD
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Natural killer (NK) cell, Flow cytometry (FC), Cytotoxicity, Reference interval
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