BACKGROUND: Clinical observations demonstrated that COVID-19 related pneumonia 
is often accompanied by hematological and coagulation abnormalities including 
lymphopenia, thrombocytopenia, and prolonged prothrombin time. The evaluation of 
laboratory findings including coagulation and inflammation parameters may 
represent a promising approach for early determination of COVID-19 severity.
METHODS AND MATERIALS: In the present study, we aimed to identify laboratory 
parameters present upon admission in patients with COVID-19 related viral 
pneumonia and associated with an early in-hospital development of refractory 
respiratory failure or severe acute respiratory distress syndrome requiring 
treatment in an intensive care unit. We investigated differences in the 
C-reactive protein (CRP) and fibrinogen levels, prothrombin time (PT) and 
international normalized ratio (INR) between COVID-19 patients who had been 
transferred to an ICU within two weeks after admission (n = 82) and COVID-19 
patients with stable course of the disease (n = 74).
RESULTS: Multiple comparisons showed statistically significantly prolonged PT on 
admission in ICU-transferred COVID-19 patients (14.15 sec, median, CI 95% 
13.4 ÷ 14.9) compared to the stable COVID-19 patients (13.25 sec, median, CI 95% 
12.9 ÷ 13.6) (p-value = .0005). CRP levels upon admission were statistically 
significantly higher in ICU-transferred COVID-19 patients (132 mg/L, median, 
CI95% 113 ÷ 159) compared to the stable COVID-19 patients (51 mg/L, median, 
CI95% 33 ÷ 72) (p-value < .0001). On-admission fibrinogen and INR levels did not 
statistically significantly differ between ICU-transferred COVID-19 patients and 
stable COVID-19 patients.
CONCLUSION: We suggest that CRP and PT levels present on admission in COVID-19 
patients may be used as early prognostic markers of severe pneumonia requiring 
transfer to ICU.