The Coronavirus Disease 2019 (COVID-19), that results of Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) infection, manifests with dysfunction of hemostasis and thrombosis. This study aims to evaluate laboratory parameters of hemostasis in hospitalized individuals with suspected COVID-19.

Individuals aged 18 years or older with suspected COVID-19 admitted to two hospitals were invited to participate in this study. The study inclusion period was from April 2020 to March 2021. The study was approved by the institutional ethics committees. The diagnosis of COVID-19 was confirmed by positive SARS-CoV-2 real-time reverse-transcription polymerase chain reaction. Antithrombin, factor V, factor VII, factor XI, factor XII, factor XIII and prothrombin assays were performed using the Multiplex immunoassay technique (ThermoFisher Scientific, Vienna, Austria). Propensity score matching for sex and age were estimated by a logistic regression model for COVID-19 and non-COVID-19 individuals in the R software. The proportions found in each group were compared by Fisher's exact test, when the variable was categorical, and by the Mann-Whitney test, when it was continuous. Linear regression was performed adjusting the levels of clotting factors and antithrombin for the severity score (Sequential Organ Failure Assessment - SOFA). Correlation between SOFA, clotting factors and antithrombin in individuals with COVID-19 were performed by using the Spearman test. Only very strong correlations (≥0.9) were considered; p-value<0.05 was considered statistically significant.

A total of 151 individuals were included in the study, of whom 138 (91.4%) with the diagnosis of COVID-19 and 13 (8.6%) non-COVID-19. After 2:1 matching, 26 individuals with COVID-19 and 13 non-COVID-19 participated in the study. In the univariate analysis, the group of COVID-19 had higher levels of antithrombin, factor V, factor VII, factor XI and prothrombin compared to the non-COVID-19 group. However, after adjusting for SOFA, only the levels of factor XI and prothrombin remained different between the groups (higher in the COVID-19) (p=0.04 and p=0.04, respectively). We found no association between factor XI and prothrombin with mortality. However, we found a very strong correlation between coagulation factors V and VII (r=0.923, p<0.0001).

Our results show that plasma levels of antithrombin, factor V, factor VII, factor XI and prothrombin were higher in the COVID-19 when compared with non-COVID-19 group of critically-ill patients, but the difference was lost after adjusting the analysis for SOFA. Only the levels of factor XI and prothrombin remained significant in the COVID-19 group after adjustment. This finding suggests that the severity of the disease rather than viral etiology was the main determinant of the difference in the plasma levels of these proteins. We also showed a strong correlation between factor V and VII in our study. Indeed, factor VII is the major trigger of coagulation in vivo. Therefore, it is possible that factor V and VII could act together to boost coagulation and promote thrombus formation in patients with COVID-19.

Our study suggests that increased levels of procoagulant factors in hospitalized critically-ill individuals with suspected COVID-19 are rather related to disease severity than to its cause.