Reduction of lymphocyte at early stage elevates severity and death risk of COVID-19 patients: a hospital-based case-cohort study

Fei, Jun; Fu, Lin; Li, Ying; Xiang, Hui-Xian; Xiang, Ying; Li, Meng-Die; Liu, Fang-Fang; Xu, De-xiang; Zhao, Hui

Background and objective: Severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2)-induced coronavirus disease 2019 (COVID-19) has been pandemic worldwide. Several reports observed a reduction of lymphocytes among COVID-19 patients. However, clinical significance of lymphocyte reduction in COVID-19 patients remains unclear. The objective of this study was to analyze the association between lymphocyte reduction at early stage and the prognosis of COVID-19 patients. Methods: All 192 hospitalized patients with COVID-19 were enrolled. Electronic medical records, including demographic data, clinical characteristics, comorbidities and exposure history, were collected. Biochemical indexes on admission and chest computed tomography (CT) were detected. Patient's prognosis was followed up. Results: On admission, 84 (43.8%) patients suffered from lymphocyte reduction among COVID-19 patients. The count and percentage of lymphocytes on admission were lower among more than seventy-year-old patients than those of younger patients. Multivariate logistic regression revealed that older age was a risk factor of lymphocyte reduction. Of interest, chest CT score, a key marker of lung injury, was increased among COVID-19 patients with lymphocyte reduction. By contrast, PaCO2, SpO2 and oxygenation index, several respiratory function markers, were decreased in COVID-19 patients with lymphocyte reduction. Moreover, TBIL and DBIL, two markers of hepatic injury, creatinine and urea nitrogen, two indices of renal function, and creatine kinase, AST and LDH, three myocardial enzymes, were elevated in COVID-19 patients with lymphocyte reduction. Among 84 COVID-19 patients with lymphocyte reduction, 32.1% died. Fatality rate was obviously higher in COVID-19 patients with lymphocyte reduction than those with normal lymphocyte (RR=5.789, P<0.001). Conclusion: Older COVID-19 patients are more susceptible to lymphocyte reduction. Lymphocyte reduction at early stage aggravates the severity of multiple organ injuries and elevates death risk of COVID-19 patients.