Persistent lymphopenia after diagnosis of COVID-19 predicts acute respiratory distress syndrome: A retrospective cohort study

Background Lymphopenia is a marker of immunosuppression after severe coronavirus disease-2019 (COVID-19) which is characterized by acute respiratory distress syndrome (ARDS). This study aimed to evaluate the relationships between persistent lymphopenia and ARDS. Methods A retrospective cohort study of 125 patients with COVID-19 admitted to government-designated treatment center between 14 January 2020, and 20 March 2020 was conducted. We recorded all complete blood cell counts during the day 0th, 3rd, and 7th following the diagnosis of COVID-19. Patients were grouped based on the depression of the lymphocyte cell count, their return, or their failure to normal. The primary outcome was the occurrence of ARDS, and secondary outcomes included developing vital organ dysfunction and hospital lengths of stay. Results 17.6% (22/125) patients developed ARDS. The lymphocyte counts with ARDS and non-ARDS were 0.94 x 109/L, 1.20 x 10(9)/L at admission, respectively (p = 0.02). On the 3rd and 7th day, the median of lymphocyte count in ARDS was significantly lower than that of non-ARDS. Multivariable logistic regression, which was adjusting for potentially confounding factors (including age, comorbidities, and APACHE II score), showed that persistent lymphopenia within the 7th day was independently associated with ARDS (OR, 3.94 [95% CI, 1.26-12.33, p = 0.018). Further, patients with persistent lymphopenia had longer hospital lengths of stay (p < 0.001). Conclusion The results showed persistent lymphopenia predicted ARDS after COVID-19. Further studies are needed to investigate whether immunostimulation of lymphocytes within 1 week can reduce ARDS occurrence in patients with COVID-19.