Comparison of Clinical Features between Critically and Non-Critically Ill Patients In SARS and COVID-19: A Systematic Review and Meta-Analysis

Background: The predictors for critical illness of severe acute respiratory syndrome (SARS) and coronavirus disease 2019 (COVID-19) have not been identified. We aimed to compare differences in clinical characteristics between critically and non-critically ill patients with SARS and COVID-19, respectively. Methods: PubMed, EMBASE, and medRxiv were retrieved for clinical studies on confirmed cases of SARS and COVID-19 up to March 15, 2020. Any study with more than 10 patients including rate of critically ill patients with SARS or COVID-19 was eligible for inclusion. Clinical characteristics were recorded from the eligible articles. The rate of critical cases was estimate and clinical features were compared between the critically and non-critically ill patients for both SARS and COVID-19 group. Findings: A total of 24 eligible articles with 1208 patients for SARS and 1800 for COVID-19 were identified. The pooled prevalence of critically ill cases was 29% (95% CI: 24% to 34%) for SARS and 17% (95% CI: 12% to 21%) for COVID-19. For both SARS and COVID-19, critically ill patients were older and had a higher frequency of men and cardiovascular disease than non-critically ill patients (all P<0.05). Patients with critical illness had significantly higher neutrophil count (MD= 1.42, 95% CI: 0.31 to 2.52, P = 0.01, I2 = 0% for SARS; MD= 1.59, 95% CI: 0.17 to 3.01, P = 0.03, I2 = 73% for COVID-19) and lower lymphocyte count (MD= -0.15, 95% CI: -0.29 to -0.02, P = 0.03, I2 = 0% for SARS; MD= -0.41, 95% CI: -0.54 to -0.27, P < 0.001, I2 = 72% for COVID-19) than patients without critical illness for both SARS and COVID-19. Additionally, a lower level of CD3 + and CD4 + , a higher level of D-dimer as well as longer prothrombin time, and more lactate dehydrogenase and creatinine were found in critically ill patients with COVID-19 (all P<0.05). Interpretation: Males, patients with older age, comorbidities, or higher neutrophil counts, and lower lymphocyte counts tended to develop critical illness. Level of CD3 + , CD4 + , D-dimer, lactate dehydrogenase and creatinine, and prothrombin time were newly identified indicators for critical illness for COVID-19. Funding Statement: This study was funded by the 1·3·5 project for disciplines of excellence, West China Hospital, Sichuan University (ZYGD18013), which helped with writing and data collection. Declaration of Interests: The authors declare no competing interests. Ethics Approval Statement: PRISMA guidelines were utilized.