ABSTRACT
Background: Coronavirus disease 2019 (COVID-19) has rapid spread worldwide and its pathogenesis is still not well understood. It's critical to identify the key immune inflammatory markers that may be correlated with COVID-19 severity. Objective: This study aimed to study the association of the peripheral lymphocyte subsets' alteration and IL-6 serum level with disease severity and outcome in COVID-19. Methodology: Samples from 30 COVID-19 patients were collected;one is EDTA anticoagulated for flowcytometric analysis of different lymphocyte subsets and the other for Interleukin-6 (IL6) serum level assessed by ELISA technique. Results: Absolute lymphocytic count (0.9 (0.5-1.4)× 103/µL), CD4+ T cells (217 (135.6-445.5) cells/µL), CD8+ T cells (160 (112-338) cells/µL) and natural killer (NK) cells (33.3 (18.2-99.5) cells/µL) were significantly reduced in severe COVID-19 patients with significantly elevated IL-6 serum levels 90 (70-120) (pg/mL) in severe patients. Lower T lymphocytes and NK subset counts with higher IL-6 levels were significantly associated with higher mortality. However, B cell count was not associated with severity or mortality. Il-6 levels, CD4+ and CD8+ T cells counts were considered best predictors of disease severity and mortality according to ROC curve analysis (with AUC 0.842, 0.884 and 0.773 respectively). Conclusion: Peripheral lymphocyte subsets as CD4+ T cells, CD8+ T cells and NK cells were significantly reduced in severe COVID-19 patients. CD4+ T cell count was the most significant biomarker for disease severity.Serum IL-6 levels were higher in severe illness. So, IL-6 can serve as a significant predictor of COVID-19 severity. As regard mortality and relation with lymphocytic count and lymphocytic subsets, total lymphocytic count and all T lymphocyte subsets CD4+, CD8+ and CD56+ cells count can be used as a significant predictor of death in COVID-19 patients. However, CD19+ cells counts had no relation with death. © 2020 The author (s). Published by Zagazig University.