Annals of Laboratory Medicine

Korean Society for Laboratory Medicine (대한진단검사의학회)
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Peripheral White Blood Cell Dynamics as a Biomarker of Coronavirus Disease Severity

  • Joung Ha Park (Division of Infectious Diseases, Department of Internal Medicine, Chung-Ang University Gwangmyeong Hospital) ;
  • Hyemin Chung (Division of Infectious Diseases, Department of Internal Medicine, Chung-Ang University Gwangmyeong Hospital) ;
  • Min-Chul Kim (Division of Infectious Diseases, Department of Internal Medicine, Chung-Ang University Gwangmyeong Hospital) ;
  • Seong-Ho Choi (Division of Infectious Diseases, Department of Internal Medicine, Chung-Ang University Hospital) ;
  • Jin-Won Chung (Division of Infectious Diseases, Department of Internal Medicine, Chung-Ang University Hospital) ;
  • Hye Ryoun Kim (Department of Laboratory Medicine, Chung-Ang University Hospital)
  • Received : 2025.04.21
  • Accepted : 2025.09.30
  • Published : 2026.05.01
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Abstract

Background: Despite widespread vaccination efforts against severe acute respiratory syndrome coronavirus 2, variants with increased transmissibility or immune evasion continue to emerge, posing a considerable challenge. Understanding the immunological factors associated with coronavirus disease (COVID-19) progression is essential for improving patient management and treatment strategies. We explored the dynamic changes in the peripheral white blood cell (WBC) profile, including T lymphocyte subsets, to assess their potential as predictors of disease severity and progression. Methods: Two hundred fifty-eight patients hospitalized for confirmed COVID-19 were classified into four sub-cohorts based on changes in disease severity over 7 days. WBC parameters, including absolute neutrophil, total lymphocyte, and T cell subset counts, and the neutrophil-to-lymphocyte ratio (NLR) were assessed at admission and after 7 days. Results: Patients with persistent mild-to-moderate illness exhibited a marked increase in the lymphocyte count and a decrease in the NLR over time. In contrast, patients with sustained severe-to-critical illness showed an increasing WBC count without a corresponding increase in the lymphocyte count, in addition to a marked elevation in the NLR. Patients whose condition improved from severe-to-critical to mild-to-moderate illness showed increased cluster of differentiation (CD)3+ and CD4+ T cell counts and an elevated CD4/CD8 ratio, whereas the NLR did not significantly change. Conclusions: The early-phase dynamics of T cell subsets may serve as a useful biomarker of disease severity and recovery in patients with COVID-19. Monitoring these immunological changes may help support clinical decision-making and inform the timing of therapeutic interventions.

Keywords

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