Clinical Importance of Immunophenotyping of Peripheral Blood Lymphocyte Subsets in Adult COVID-19 Patients: A Cross-Sectional Study

Introduction: Coronavirus disease-2019 can occur with symptoms such as mild fever and cough or with symptoms such as cytokine storm and respiratory failure. Therefore, its pathogenesis continues to be investigated. In this study, we investigated the relationship between lymphocyte subsets and natural killer cell levels with disease prognosis in COVID-19 patients.Materials and Methods: We included patients positive for SARS-CoV-2 viral RNA in nasopharyngeal swab samples in the symptomatic period or COVID-19 IgM/IgG Antibody Rapid Test positive in serum samples after the second week of symptoms between May 4, 2020, and July 4, 2020. On the first day of their hospitalization, a total of 22 lymphocyte subsets from the whole blood taken from the patients were evaluated by flow cytometric examination. The clinical status of the patients is classified as asymptomatic, mild, moderate, severe, or arterial partial oxygen pressure. We compared patients' clinical and laboratory characteristics with and without pneumonia. In addition, we examined the lymphocyte subset cell levels of the patients that we classified according to their clinical status.Results: Of the patients, 38 (67%) were male, with a median age of 38 (28-49) years; 78.9%, 19.2%, 26.3%, 43.9%, 7% and 3.5% were asymptomatic, mild, moderate, severe and critical patients, respectively. Pneumonia was present in 31 (54.4%) of the patients. Mean levels of C-reactive protein (<0.001), D-dimer (p= 0.001) and lactate dehydrogenase (p= 0.021) were significantly higher in patients with pneumonia compared to patients without pneumonia. CD3(+) T cell (p= 0.015), CD4(+) T cell (p= 0.005), CD19(+) B cell (p= 0.019), CD20+ B cell (p= 0.023), and CD19 (+) CD27- B cell (p = 0.022) in asymptomatic patients were significantly higher than those with symptom. The increase in the mean levels of CD4(+)/CD8(+), CD3(+), CD4(+), CD19(+), CD20(+), HLA-DR and CD19(+)CD27(+)IgD- cells decreased the possible oxygen support by 0.129-fold, respectively (p= 0.026); 0.997 fold (p= 0.031); 0.995 fold (p= 0.018); 0.98 fold (p= 0.028); 0.979 fold (p= 0.038); 0.992 fold (p= 0.032); 0.998 fold (p= 0.037).Conclusion: Our study revealed the CD4(+)/CD8(+) ratio, CD3(+), CD4(+), CD19(+), CD20(+), HLA-DR and CD19(+)CD27(+)IgD- cell levels could be helpful markers in predicting the clinical course and prognosis by examining the largest lymphocyte subsets in adult COVID-19 patients in Turkiye.