Characteristics of peripheral blood lymphocytes and lymphocyte subsets in COVID-19 patients

Objective: To investigate the value of peripheral blood lymphocytes and lymphocyte subsets in the diagnosis of illness severity and prognosis of coronavirus disease 2019 (COVID-19) Methods: A retrospective analysis was performed on 179 COVID-19 patients admitted to the optical valley and Sino-French new branch district of Tongji Hospital in Wuhan, from February 8th, 2020 to February 18th, 2020 The included patients were divided into a mild group (n=84), a severe group (n=58) and a critical group (n=37) The median age of recruited patients was 65, including 107 males and 72 females ROC analysis was performed to determine the best threshold value of the lymphocyte subsets in distinguishing critical patients from severe or mild patients GraphPad Prism6 and SPSS19 0 statistical software were used for data analysis Differences among groups were analyzed using the Mann-Whitney U test Results: On admission, the white blood cell (WBC) of the critical patients were significantly higher than that of the mild and severe patients (P<0 001), and the lymphocytes of the mild patients were significantly higher than that of the critical and severe patients (P<0 001) The counts of T+B+NK, CD3, CD4, CD8, and NK cells were significantly decreased with the increase of illness severity (P<0 001) while the CD4/CD8 ratio in the critical group was significantly higher than that of the mild and severe groups (mild vs critical, P=0 002;severe vs critical, P=0 030) Furthermore, the receiver operating characteristic (ROC) analysis revealed that T+B+NK and CD3 showed the highest area under ROC for the identification of critical cases Then the mild and severe cases were combined into one group and compared with the critical group Neutrophil-to-lymphocyte ratio (NLR), neutrophil-to-CD3, neutrophil-to-CD4 and neutrophil-to-CD8 were used to assess illness severity, and our data showed that NLR was the best marker The lymphocytes of the mild and severe patients were increased ten days after admission with improvement of the disease However, the lymphocytes of the critical patients were progressively decreased with the deterioration of diseases Conclusions: The decrease of T+B+NK and CD3 cells, the increase of CD4/CD8 ratio and NLR serve as significant factors for identification of severe COVID-19 cases The dynamic monitoring of total lymphocytes and subsets has potential clinical value in predicting the prognosis of COVID-19