Usefulness of the New Hematological Parameter: Reactive Lymphocytes RE-LYMP with Flow Cytometry Markers of Inflammation in COVID-19.

Identification of patients with activation of the immune system which indicates the presence of infection is essential, especially in the times of the global coronavirus 2019 (COVID-19) pandemic. The aim of the present study was to evaluate the reactive lymphocytes (RE-LYMP) parameter in COVID-19 and to correlate it with activation lymphocytes markers by flow cytometry. The study group consisted of 40 patients: with COVID-19 infection (n = 20) and with others virus infections without COVID-19 (COVID-19(-) virus (n = 20)) and 20 healthy donors (HC). Blood count and flow cytometry were performed. The COVID-19(+) group had significantly lower RE-LYMP parameter than the COVID-19(-) virus group (5.45 vs. 11.05, p < 0.05). We observed higher proportion of plasmablasts in the COVID-19(+) and COVID-19(-) virus groups than HC (8.8 vs. 11.1 vs. 2.7, p < 0.05). In the COVID-19(+) there was a lower proportion of CD4+ CD38+ cells than in the other groups (significant differences between COVID-19(+) and COVID-19(-) virus groups). RE-LYMP correlated with activated T lymphocytes CD38+ and HLA-DR+ in the COVID-19(-) virus group, however in the COVID-19(+) group correlations with T lymphocytes CD25+ and CD45RO+ were observed. In summary the analysis of the RE-LYMP together with flow cytometric activation markers can be helpful in identifying and distinguishing patients with COVID-19(+) from other viruses and HC.