T-Cell Subset Counts in Peripheral Blood Can Be Used as Discriminatory Biomarkers for Diagnosis and Severity Prediction of Coronavirus Disease 2019.

This study evaluated the significance of lymphocyte subset detection in peripheral blood in the diagnosis and prognosis of coronavirus disease 2019 (COVID-19). Our results revealed that CD3+ T cells, CD4+ T cells, CD8+ T cells, and natural killer cells were significantly decreased in patients with COVID-19. These patients had a relatively slight decrease in CD4+ T cells but a severe decrease in CD8+ T cells. The significantly elevated CD4/CD8 ratio was observed in COVID-19 patients. T-cell subset counts were related to the severity and prognosis of COVID-19, suggesting that the counts of CD8+ T and CD4+ T cells can be used as diagnostic markers of COVID-19 and predictors of disease severity.