Dynamic change in lymphocyte count in the early stage is a potential predictor of the severity of COVID-19

Abstract Background Lymphopenia is associated with COVID-19 severity. Herein we describe the dynamic changes in lymphocyte count during hospitalization and explore a possible association with the severity of COVID-19.Methods In this retrospective study, 13 non-severe COVID-19 patients diagnosed at admission were enrolled. One patient progressed to severe disease. Dynamic changes in lymphocyte count and CT score of all patients were analyzed.Results Lymphocyte count changed significantly in the non-severe patients over time (admission vs day 5, P=0.685; day 5 vs day 15, P<0.001). Lymphocyte count of the severe patient fluctuated, and even decreased within the first 12 days post-admission, before increasing gradually. Chest CT scores of nine (75%) non-severe patients on the 5th day of hospitalization were higher than at admission, but decreased gradually thereafter (admission vs day 5, P<0.001, day 5 vs day 15, P=0.004). In the severe patient, CT score continued to increase for 2 weeks after admission, before decreasing gradually.Conclusions Non-severe COVID-19 patients had significantly increased lymphocyte count and decreased CT score 1 week after illness onset. Dynamic change in lymphocyte count in the early stages of COVID-19 may be helpful to identify the patients who are more likely to develop severe or critical illness.