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Letters to the Editor
levels of intensity care depending on disease severity. After the viral diagnosis, 62 patients, depending on their severity, were consecutively admitted to three wards, characterized by low-intensity care (n=21), when hypoxia could be handled by ventilation support with high-flow nasal cannulas; intermediate sub-intensive care (n=21), when hypoxia prompted the use of continuous positive airway pressure, or high-intensity care (n=20) when hypoxia warranted intubation and mechanical ven- tilation in ICU. In this context, we designed the project COHERENT (COVID-19: HEmostasis, immune Response, ENdothelial perTurbation and complement), aimed to investigate the mechanism of thrombosis in COVID-19 patients. The project received approval by Comitato Etico Area2, Milano (clinicaltrials gov. Identifier: 360_2020). Patients started prophylaxis with low-dose LMWH on admission and dosages were then adjusted by attending physicians after patient transfer to the hospital wards. LMWH dosages were as follows: low-intensity, enoxaparin 70 UI/Kg once a day; interme- diate-intensity, 70 UI/kg twice a day; high-intensity, 100
UI/kg once a day.
Venous blood was collected, not earlier than 72 hours
after the administration of LMWH prophylaxis and before the administration of the daily dose in vacuum- tubes containing 1/10 volumes of trisodium citrate 0.109 M. Specimens were centrifuged for 20 minutes at 3,000g.
Prothrombin and activated partial thromboplastin time (PT, APTT) were performed using Recombiplastin-2G and Synthasil APTT (Werfen, Orangeburg, NY, USA) with results expressed as clotting time ratios (patient-to- normal). Factor VIII (FVIII) and FII were measured by the one-stage assay based on APTT and FVIII-deficient plas- ma and PT-based assay and FII-deficient plasma, respec- tively (Werfen). von Willebrand factor antigen (VWF:Ag)
and ristocetin cofactor activity (VWF:RCo) were meas- ured by commercial kits (Werfen). Fibrinogen was meas- ured according to Clauss. D-dimer and free protein S (PS) antigen were measured by latex-based assays (Werfen). Antithrombin and protein C (PC) activity were measured by chromogenic assays (Werfen). Platelet counts and markers of inflammation and acute-phase reactions (C-reactive-protein and ferritin) were obtained from the patients’ records.
The DIC score was calculated using ISTH criteria.11 In patients with sepsis, SIC score is more sensitive than the DIC score to detect an associated coagulopathy, thus we also calculated this score that is based on platelet count, PT-international normalized ratio (PT-INR) and the Sequential Organ Failure Assessment (SOFA) score that includes data on respiratory, cardiovascular, hepatic and renal dysfunction, but also on the presence of hemostasis alterations such as thrombocytopenia and PT-INR.
Patients characteristics did not differ in the three groups. No differences for well-known risk factors and comorbidities (age, body mass index, hypertension, dia- betes) between the groups according to the intensity of care were observed. In the entire cohort we recorded three deaths and 25 thrombotic events (40%) in 25 patients, i.e., 16 deep-vein thrombosis, eight pulmonary embolism and one visceral venous thrombosis.
Median (min-max) values of the hemostasis measure- ments in COVID-19 patients are listed in Table 1. The PT-ratio was slightly increased in patients at high- and intermediate- care intensity compared with those at low- intensity care. The APTT-ratio was slightly decreased in all patients irrespective of care intensity. Median platelet counts for patients at intermediate or high-care intensity were higher than those at low-intensity; the lowest observed platelet count (80x109/L) being higher the
AB
CD
Figure 1. Box plots of results for (A) factor VIII, (B) antithrombin, (C) protein C and (D) protein S for patients at low, intermediate and high intensity of care.
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