BackgroundCoronavirus disease 2019 (COVID-19) is a novel infectious disease caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) emerged in Wuhan and has quickly spread across the world. The mortality rate in critically ill patients with COVID-19 is high. This study analyzed clinical and biochemical parameters between mild and severe patients, helping to identify severe or critical patients early.MethodsIn this single center, cross-sectional study, 143 patients were included and divided to mild/moderate and sever/critical groups. Correlation between the disease criticality and clinical features and peripheral blood biochemical markers was analyzed. Cut-off values for critically ill patients were speculated through the ROC curve.ResultsSignificantly, disease severity was associated with age (r=0.458, P<0.001), comorbidities (r=0.445, P<0.001), white cell count (r=0.229, P=0.006), neutrophil count (r=0.238, P=0.004), lymphocyte count (r=-0.295, P<0.001), albumin (r=-0.603, P<0.001), high-density lipoprotein cholesterol (r=-0.362, P<0.001), serum potassium (r=-0.237, P=0.004), plasma glucose (r=0.383, P<0.001), total bilirubin (r=0.340, P<0.001), serum amyloid A (r=0.58, P<0.001), procalcitonin (r=0.345, P<0.001), C-reactive protein (r=0.477, P<0.001), lactate dehydrogenase (r=0.548, P<0.001), aspartate aminotransferase (r=0.342, P<0.001), alanine aminotransferase (r=0.264, P=0.001), erythrocyte sedimentation rate (r=0.284, P=0.001) and D-dimer (r=0.477, P < 0.001) .ConclusionsWith the following parameters such as age>52years, C-reactive protein >64.79mg/L, lactate dehydrogenase >245U/L, D-dimer >0.96 mu g/mL, serum amyloid A>100.02mg/L, or albumin < 36g/L, the progress of COVID-19 to critical stage should be closely observed and possibly prevented. Lymphocyte count, serum potassium, high-density lipoprotein cholesterol and procalcitonin may also be a prognostic indicator.