Thromboelastography (TEG) in COVID-19 Patients - Not All Hypercoagulable

Introduction COVID-19 can lead to a severe inflammatory response and cytokine storm, which is associated with activation of blood coagulation, platelets, and endothelium leading to a severe prothrombotic state. Recent studies have interpreted TEG parameters of increased maximum amplitude (MA) and alpha angle (AA) as indicating a hypercoagulable pattern in patients with COVID-19. The definition of hypercoagulability in literature has been variable while some have used increased MA, others used increased coagulation index (CI) as a surrogate for a hypercoagulable state. Here we report our center experience using TEG to evaluate coagulation in COVID-19 patients. Methods Retrospective analysis of 37 critically ill patients that were evaluated using TEG on a single occasion along with standard coagulation tests. We defined hypercoagulable pattern as CI > 3;hypocoagulable pattern was defined as CI <-3;and normal pattern if CI was between-3-3. Results TEG patterns were interpreted as hypercoagulable in 5 (13.5%), normal in 22 (59.5%) and hypocoagulable in 10 (27%) patients using the TEG coagulation index (CI). MA and AA were elevated in 13 (35.1%) and 10 (27%) patients, respectively, and both were elevated in 8 (21.6%). Discussion Our results show a normal TEG pattern in most of our critically ill COVID-19 patients based on CI (Figure 1);only 5 (13.5%) showed a hypercoagulable pattern. These findings differ from previous reports of TEG in COVID-19 patients, where a hypercoagulable TEG pattern was shown in 83-90% of patients, in these reports interpretation of hypercoagulability was based on AA or MA. We used the CI to define a hypercoagulable state, which has been used to define hypercoagulability in orthopedic surgery and during pregnancy. An elevated MA or AA was seen in only 15 (40%) of our patients. Plasma fibrinogen, an acute-phase reactant, is also elevated in COVID-19 patients. The mean fibrinogen level in our patients was 364 mg/dl, which is lower than those reported by Panigada and Mortus, where mean fibrinogen levels were 680 and 740 mg/dl, respectively. The high MA may reflect the high fibrinogen observed in COVID-19 patients and this may explain the differences in the number of patients considered as “hypercoagulable” in our cohort compared to others. Conclusion;Our study in COVID-19 patients advances a caution in the interpretation of TEG parameters and its use as an indicator of a hypercoagulable state in COVID-19 patients.