Investigation of differences in coagulation characteristics between hospitalized patients with SARS-CoV-2 Alpha, Delta, and Omicron variant infection using rotational thromboelastometry (ROTEM): A single-center, retrospective, observational study.

BACKGROUND: The severe acute respiratory syndrome coronavirus 2 Omicron variant has a low rate of serious illness, is highly contagious, and has spread rapidly since January 2022. The number of severe cases and deaths remains problematic. Here, we aimed to elucidate the coagulation pathology of Omicron-infected patients using rotational thromboelastometry.

METHODS: Patients with coronavirus disease 2019, hospitalized and treated from January 2021 to April 2022, were included. The Alpha-Delta and Omicron groups were defined during admission. Blood tests, clinical course, and rotational thromboelastometry measurements were compared using a propensity score-matched cohort.

RESULTS: Both groups had 21 patients each. Lactate dehydrogenase (Alpha-Delta group [interquartile range] vs. Omicron group [interquartile range]; 449 [368-518] U/L vs. 241 [196-398] U/L, p = 0.01) and ferritin (1428 [1145-3061] ng/dl vs. 481 [188-881] ng/dl, p = 0.0002) levels were significantly lower in the Omicron group. In rotational thromboelastometry, the thrombus hardness indexes FIBTEM A5 (29 [23-34] mm vs. 23 [18-28] mm, p = 0.034) and maximum clot firmness (34 [27-40] mm vs. 26 [21-33] mm, p = 0.021) were significantly lower in the Omicron group, whereas the fibrinolysis index FIBTEM LI60 (98 [92-100] % vs. 100 [100-100] %, p = 0.0082) was higher.

CONCLUSION: Severe coagulation abnormalities may be less likely in Omicron-infected patients than in those infected with the previous Alpha and Delta variants.