A low level of CD16(pos) monocytes in SARS-CoV-2 infected patients is a marker of severity

Objectives: Severe forms of coronavirus disease 2019 (COVID-19) are characterized by an excessive production of inflammatory cytoldnes. Activated monocytes secrete high levels of cytoldnes. Human monocytes are divided into three major populations: conventional (CD14(pos)CD16(neg)), non-classical (CD14(dim)CD16(pos)), and intermediate (CD14(pos)CD16(pos)) monocytes. The aim of this study was to analyze whether the distribution of conventional (CD16(neg)) and CD16(pos) monocytes is different in patients with COVID-19 and whether the variations could be predictive of the outcome of the disease. Methods: We performed a prospective study on 390 consecutive patients referred to the Emergency Unit, with a proven diagnosis of SARS-CoV 2 infection by RT-PCR. Using the CytoDiff (TM) reagent, an automated routine leukocyte differential, we quantified CD16(neg) and CD16(pos) monocytes. Results: In the entire population, median CD16(neg) and CD16(pos) monocyte levels (0.398 and 0.054x10(9)/L, respectively) were in the normal range [(0.3-0.7x10(9)/L) and (0.015-0.065x10(9)/L), respectively], but the 35 patients in the intensive care unit (ICU) had a significantly (p<0.001) lower CD16(pos) monocyte count (0.018 x 10(9)/L) in comparison to the 70 patients who were discharged (0.064 x 10(9)/L) or were hospitalized in conventional units (0.058 x 10(9)/L). By ROC curve analysis, the ratio [absolute neutrophil count/CD16(pos) monocyte count] was highly discriminant to identify patients requiring ICU hospitalization: with a cut-off 193.1, the sensitivity and the specificity were 74.3 and 81.8%, respectively (area under the curve= 0.817). Conclusions: Quantification of CD16(pos) monocytes and the ratio [absolute neutrophil count/CD16(pos) monocyte count] could constitute a marker of the severity of disease in COVID-19 patients.

Automated summary

This study found that a decrease in CD16(pos) monocyte count is associated with the severity of COVID-19. The ratio of absolute neutrophil count to CD16(pos) monocyte count can serve as a useful marker for predicting the need for ICU hospitalization in patients with COVID-19.