BACKGROUND: Laboratory parameter abnormalities are commonly observed in COVID-19 
patients; however, their clinical significance remains controversial. We 
assessed the prevalence, characteristics, and clinical impact of laboratory 
parameters in COVID-19 patients hospitalized in Daegu, Korea.
METHODS: We investigated the clinical and laboratory parameters of 1,952 
COVID-19 patients on admission in nine hospitals in Daegu, Korea. The average 
patient age was 58.1 years, and 700 (35.9%) patients were men. The patients were 
classified into mild (N=1,612), moderate (N=294), and severe (N=46) disease 
groups based on clinical severity scores. We used chi-square test, multiple 
comparison analysis, and multinomial logistic regression to evaluate the 
correlation between laboratory parameters and disease severity.
RESULTS: Laboratory parameters on admission in the three disease groups were 
significantly different in terms of hematologic (Hb, Hct, white blood cell 
count, lymphocyte%, and platelet count), coagulation (prothrombin time and 
activated partial thromboplastin time), biochemical (albumin, aspartate 
aminotransferase, alanine aminotransferase, lactate, blood urea nitrogen, 
creatinine, and electrolytes), inflammatory (C-reactive protein and 
procalcitonin), cardiac (creatinine kinase MB isoenzyme and troponin I), and 
molecular virologic (Ct value of SARS-CoV-2 RdRP gene) parameters. Relative 
lymphopenia, prothrombin time prolongation, and hypoalbuminemia were significant 
indicators of COVID-19 severity. Patients with both hypoalbuminemia and 
lymphopenia had a higher risk of severe COVID-19.
CONCLUSIONS: Laboratory parameter abnormalities on admission are common, are 
significantly associated with clinical severity, and can serve as independent 
predictors of COVID-19 severity. Monitoring the laboratory parameters, including 
albumin and lymphocyte count, is crucial for timely treatment of COVID-19.