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INTRODUCTION: COVID-19 is associated with an increased thromboembolic risk. However, the mechanisms triggering clot formation in those patients remain unknown. PATIENTS AND METHODS: In 118 adult Caucasian severe but non-critically ill COVID-19 patients (median age 58 years; 73 % men) and 46 controls, we analyzed in vitro plasma thrombin generation profile (calibrated automated thrombogram [CAT assay]) and investigated thrombophilia-related factors, such as protein C and antithrombin activity, free protein S level, presence of antiphospholipid antibodies and factor V Leiden R506Q and prothrombin G20210A mutations. We also measured circulating von Willebrand factor (vWF) antigen and a disintegrin and metalloproteinase with a thrombospondin type 1 motif, member 13 (ADAMTS13) antigen and activity. In patients, blood samples were collected on admission to the hospital before starting any therapy, including heparin. Finally, we examined the relationship between observed alterations and disease follow-up, such as thromboembolic complications. RESULTS: COVID-19 patients showed 17 % lower protein C activity, 22 % decreased free protein S levels, and a higher prevalence of positive results for IgM anticardiolipin antibodies. They also had 151 % increased vWF, and 27 % decreased ADAMTS13 antigens compared with controls (p < 0.001, all). On the contrary, thrombin generation potential was similar to controls. In the follow-up, pulmonary embolism (PE) occurred in thirteen (11 %) patients. They were characterized by a 55 % elevated D-dimer (p = 0.04) and 2.7-fold higher troponin I (p = 0.002) during hospitalization and 29 % shorter time to thrombin peak in CAT assay (p = 0.009) compared to patients without PE. CONCLUSIONS: In COVID-19, we documented prothrombotic abnormalities of peripheral blood. PE was characterized by more dynamic thrombin generation growth in CAT assay performed on admittance to the hospital.

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In this study, we present the first case of a 34-year-old Surinamese female with ischemic retinopathy and increased free protein S due to C4BP deficiency. Possibly, the low PS/C4BP complex level has increased the risk of arterial thrombosis in our patient.

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Protein S (PS) is a Vitamin K-dependent protein that functions as a cofactor for the regulation of the coagulation system. PS works in conjunction with Activated Protein C to inactivate factors V and VIII. PS circulates in plasma either complexed to the complement protein, C4b Binding Protein or unbound. The unbound (or free) component is the functional form for the regulation of the coagulation system. PS can be measured in plasma by functional activity, the free (or unbound form) or both free and bound fractions (Total PS). The test most widely used for clinical evaluations is the Free PS Antigen assay (which is the surrogate of PS anticoagulant activity) and represents the protocol described in this chapter. The Free PS Antigen assay is an immunologic assay which specifically measures the unbound fraction of PS in test plasma. Other methods for assessing PS are also available, including PS activity and total PS Antigen assays, but protocols for these assays are not provided.

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We carried out a retrospective cohort study to construct reference ranges for free protein S (FPS) levels during pregnancy and identify any conditions or factors that may affect FPS levels. Patients that were ordered thrombophilia screening tests during gestational period were identified. Patients demonstrated to have hereditary or acquired thrombophilia were excluded. Reference ranges were constructed using regression analysis. Outcome of the index pregnancy and pregnancy complications was used to identify any confounding factors. A total of 455 pregnant women were included. The quadratic equation for FPS according to gestational age (GA) was [75.497 + (-1.516*GA) + 0.018*GA*GA]. FPS level and GA were negatively correlated (Spearmans rho statistic [rs] = -0.436, p = 0.001). FPS level and fetal growth restriction (FGR) were negatively correlated ([rs] = -0.093, p = 0.049). FPS level and placental abruption were positively correlated ([rs] = 0.098, p = 0.039). Stepwise linear regression model constructed to predict FPS level with gestational age, placental abruption and FGR as the predictor variables. Gestational age was the only variable retaining statistically significant relation with FPS level (χ(2) = 0.216, df = 3, p = 0.001). FPS levels decrease significantly throughout gestation in gravidas without hereditary and/or acquired thrombophilias. In patients without thrombophilia FPS levels are not associated with pregnancy complications. The obtained reference intervals may be useful for the clinicians ordering FPS during pregnancy.

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INTRODUCTION: Antithrombin (AT) deficiency is associated with an increasing risk of thrombosis. MATERIALS AND METHODS: 15 unrelated patients with AT deficiency defined by thrombophilic assays were recruited and detailed clinical information about patients, focusing on the personal and family history of thromboembolism (TE), were recorded. Mutation analysis was performed by direct sequencing of an AT gene (SERPINC1) in the patients and their family members. RESULTS: A total of 15 heterozygous causative mutations, each being identified in one family, were identified. Five mutations (33.3%) were reported here for the first time, including three null mutations (Ser36X, Lys70X and Try307X) and two missense mutations (Phe123Cys and Leu340Phe) probably impairing the structural integrity and stability of protein based on the AT structural analysis. Of the 15 patients, 33.3% (5/15) had additional risk factors and only one patient presented with additional genetic alteration causing an early onset of thrombosis. Fourteen patients (93.9%) suffered from multisite recurrent thrombotic episodes after a first episode of thrombosis. 93.3% of the patients experienced deep vein thrombosis (DVT) and 40.0% presented with mesenteric venous thrombosis (MVT). In addition, both venous and arterial thrombosis was present in two unrelated patients. 51.0% subjects with AT deficiency in the 15 unrelated pedigrees experienced TE events. CONCLUSIONS: Prophylactic anticoagulation may be suggested in AT-deficient patients to avoid the recurrent and multisite thrombosis. The association of primary MVT and AT deficiency is highlighted.

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La proteína S (PS) regula el sistema de coagulación mostrando actividad de cofactor de la Proteína C activada (PCa) con la cual forma un complejo equimolecular. En presencia de iones calcio este complejo inactiva por proteólisis los factores V y VIII activados por trombina. La proteína S plasmática circula 40% libre (fracción que presenta actividad de cofactor de la PCa) y 60% unida al C4-BP (proteína ligante de la fracción C4 del complemento). El objetivo fue comparar el dosaje de PS realizado por método coagulable e inmunoturbidimétrico e investigar cómo las variables preanalíticas afectan los niveles de PS determinados. Se obtuvieron los siguientes resultados: método coagulable: CV intra ensayo: (n=20): 4%, CV interensayo (n=20, 3 días): 3,4%. Método inmunoturbidimétrico: CV intraensayo (n=20): 3,7%.CV Inter. ensayo (n=20,3 días): 4,5%. Existe buena correlación (R2=0,94) entre ambos métodos, cuando la calibración por el método coagulable se realiza en la misma corrida analítica que las muestras. Cuando se realizó el estudio de Bland y Altman los dos métodos mostraron ser comparables en todos los niveles de PS estudiados. No se observaron diferencias significativas entre las muestras determinadas frescas y conservadas a -20 y -80 °C descongeladas solo una vez.

Protein S has an essential anticoagulant function acting as activated Protein C cofactor and forming an equimolecular complex with it. In the presence of calcium this complex regulates the coagulation process inactivating thrombin activated factors V and VIII by proteolysis. In plasma there are two different forms: a) free Protein S which acts as the cofactor of activated protein C (representing about 40% of total Protein S) and b) C4-BP(C4 binding protein) bound protein S which exhibits no activity as cofactor of activated Protein C (representing about 60% of total PS). The objetive was to compare the PS dosage determination by two methods: immunoturbidimetric and clotting, and to investigate how pre-analytical variables affect the results. The following results were obtained: Clotting method: CV intra assay: (n=20): 4%, CV interassay (n=20, 3 days): 3.4%; immunoturbidimetric method CV intra assay (n=20): 3.7%: CV inter assay (n=20.3 days): 4.5%. There is a good correlation (R2 = 0.94) between both methods; when the clotting method is calibrated in batch with the samples. There is significant difference between fresh and frozen ( -20 °C and -80 °C) samples when the latter have been desfrozen only once.

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BACKGROUND: Coagulation abnormalities account for 1% to 5% of the causes of adult stroke. The importance of pro-thrombotic condition as a cause of stroke has been the subject of intense controversy. The role of protein S deficiency in the etiology of stroke and the clinical pattern of cerebral infarction caused by the prothrombotic state are still unclear. We investigated clinical characteristics of cerebral infarction caused by free protein S (FPS) deficiency. METHODS: We enrolled patients with cerebral infarction over 2 years. Cerebral infarction was classified into transient ischemic attack, lacunar infarction, embolic infarction, and thrombotic infarction. We assayed free protein S, prothrom-bin time (PT), and activated partial thromboplastin time (APTT) within 24 hours after stroke and measured free protein S and protein S Ag at 3 months after cerebral infarction. All patients underwent a cardiological examination and neu-roimaging study, and cerebral angiography was done only when necessary. RESULTS: Eight patients (1.67%) among 474 patients with cerebral infarction had FPS deficiency as a cause of stroke. Four were male and four were female. The history of venous thrombosis was not noted. The age of patients were from 24 to 83 years old at the time of stroke. Two patients had family members with FPS deficiency. The types of stroke were variable, such as thrombotic infarction in 3 patients, lacunar infarction in 4 patients, and embolic infarction in one patient. Cerebral arterial stenosis was noted in 3 patients. Other associated risk factors of stroke were smoking, hypertension, pregnancy, low HDL cholesterol, sinus bradycardia, left ventricular hypertrophy on EKG, and old age. All patients had normal PT, APTT, and liver function test. CONCLUSIONS: FPS deficiency can be a risk factor for cerebral infarction in young patients as well as old patients. Free protein S (FPS) deficiency may increase risk of cerebral infarction in the presence of other risk factors of stroke but this requires confirmation by a large study in unselected patients.

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Antithrombin III deficient individuals have an increased risk of venous thrombosis and thromboembolism at a young age. To our knowledge, cerebral venous thrombosis associated with antithrombin III deficiency has not yet been reported in Korea. A 27-year-old pregnant woman without any known stroke risk factors was admitted to our hospital because of convulsions. Brain MRI and MR venography showed dural sinus thrombosis of the superior sagittal sinus, straight sinus, and left lateral sinus with venous hemorrhagic infarctions in both frontal and parietal lobes. Antithrombin III concentrations were decreased to 37%. We speculated that the etiology of the cerebral venous thrombosis in this patient was associated with antithrombin III deficiency. We suggest that antithrombin III deficiency should be considered as a possible cause of cerebral venous thrombosis.

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