Objective. To study changes in blood coagulation during COVID-19 infection complicated treatment of children with hemoblastoses.

Materials and methods. Clinical and laboratory data of 33 patients aged 2 to 18 years (median — 7 years) with COVID-19 infection, which complicated the treatment of oncohematological disease, are presented. Three groups of patients were identified at the time of detection of the infection. The first group included 16 patients with asymptomatic (3) and mild (13) forms of COVID-19 infection. The second group — 7 patients of moderate severity (non-severe pneumonia with radiographically confirmed without RDS and without respiratory failure). The third group — 10 patients with severe pneumonia confirmed by X-ray and respiratory failure requiring respiratory support.

Results. An increase in the activity of factor VIII in patients of the first and second groups correlated with an increase in the activity (G=0.772; p=0.0001) and the content (G=0.511; p=0.031) of von Willebrand factor. In patients of the third group the activity of factor VIII was 198.0 [155.0—347.0] % and the activity of von Willebrand factor was 220.0 [16.05—326.0] % exceeded the values of the corresponding indicators (130.9 [98.0—147.8] % (p=0.026) and 174.0 [108.0—226.0] % (p=0.053) in children of the first group. The activation of coagulation controlled by inhibitors was accompanied by a trend towards a decrease in the activity of antithrombin III to 89.0 [55.0—118.0] % (p=0.045), protein C to 61.0 [26.0—88.0] % (p=0.093) and protein S up to 80.0 [52.0—97.0] % (p=0.0544) compared with patients of the first group and controls (p<0.05). Subsequently catheter-associated thrombosis complicated the treatment of 2 patients of the third group. At the time of detection of thrombosis factor VIII activity exceeded 250 %, and protein S activity was less than 50 %. The ratio of factor VIII activity to protein S activity was 3.1 [2.7—3.5] and it was the highest.

By the 180th day after the registration of COVID-19 infection the studied blood coagulation parameters still did not reach the normal values. The activity of factor VIII in patients of group 1 was 112 [89—197] % and group 2 was 127 [90—154] % and exceeded indicators of the control group (87.0 [60.0—154.0] %). Similarly the increase in the von Willebrand factor antigen in patients of group 1 was 107 [87—158] % and group 3 was 113 [78—128] % compared with the control (92 [87.0—105.0] %).

Conclusion. The revealed changes in the activity of factor VIII, the content and activity of the von Willebrand factor in children with hemoblastoses can be considered as a marker of the severity of the COVID-19 infection. Uncontrolled, due to a decrease in the activity of protein S, an increase in the activity of factor VIII, more than 2.5 times, can be considered as indications for anticoagulant prevention of thrombosis of the great vessels.