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. 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). 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 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.