Effect of weight-adjusted intermediate-dose versus fixed-dose prophylactic anticoagulation with low-molecular-weight heparin on venous thromboembolism among noncritically and critically ill patients with COVID-19: the COVI-DOSE trial, a multicenter, randomised, open-label, phase 4 trial.

Background: Venous thromboembolism is a major complication of coronavirus disease 2019 (COVID-19). We hypothesized that a weight-adjusted intermediate dose of anticoagulation may decrease the risk of venous thromboembolism COVID-19 patients. Methods: In this multicenter, randomised, open-label, phase 4, superiority trial with blinded adjudication of outcomes, we randomly assigned adult patients hospitalised in 20 French centers and presenting with acute respiratory SARS-CoV-2. Eligible patients were randomly assigned (1:1 ratio) to receive an intermediate weight-adjusted prophylactic dose or a fixed-dose of subcutaneous low-molecular-weight heparin during the hospital stay. The primary outcome corresponded to symptomatic deep-vein thrombosis (fatal) pulmonary embolism during hospitalization (COVI-DOSE ClinicalTrials.gov number: NCT04373707). Findings: Between May 2020, and April 2021, 1000 patients underwent randomisation in medical wards (noncritically ill) (80.1%) and intensive care units (critically ill) (19.9%); 502 patients were assigned to receive a weight-adjusted intermediate dose, and 498 received fixed-dose thromboprophylaxis. Symptomatic venous thromboembolism occurred in 6 of 502 patients (1.2%) in the weight-adjusted dose group and in 10 of 498 patients (2.1%) in the fixed-dose group (subdistribution hazard ratio, 0.59; 95% CI, 0.22-1.63; P = 0.31). There was a twofold increased risk of major or clinically relevant nonmajor bleeding: 5.9% in the weight-adjusted dose group and 3.1% in the fixed-dose group (P = 0.034). Interpretation: In the COVI-DOSE trial, the observed rate of thromboembolic events was lower than expected in patients hospitalized for COVID-19 infection, and the study was unable to show a significant difference in the risk of venous thromboembolism between the two low-molecular-weight-heparin regimens. Funding: French Ministry of Health, CAPNET, Grand-Est Region, Grand-Nancy Métropole.

Strategies to safely rule out pulmonary embolism in COVID-19 outpatients: a multicenter retrospective study.

OBJECTIVES: The objective was to define a safe strategy to exclude pulmonary embolism (PE) in COVID-19 outpatients, without performing CT pulmonary angiogram (CTPA). METHODS: COVID-19 outpatients from 15 university hospitals who underwent a CTPA were retrospectively evaluated. D-Dimers, variables of the revised Geneva and Wells scores, as well as laboratory findings and clinical characteristics related to COVID-19 pneumonia, were collected. CTPA reports were reviewed for the presence of PE and the extent of COVID-19 disease. PE rule-out strategies were based solely on D-Dimer tests using different thresholds, the revised Geneva and Wells scores, and a COVID-19 PE prediction model built on our dataset were compared. The area under the receiver operating characteristics curve (AUC), failure rate, and efficiency were calculated. RESULTS: In total, 1369 patients were included of whom 124 were PE positive (9.1%). Failure rate and efficiency of D-Dimer > 500 µg/l were 0.9% (95%CI, 0.2-4.8%) and 10.1% (8.5-11.9%), respectively, increasing to 1.0% (0.2-5.3%) and 16.4% (14.4-18.7%), respectively, for an age-adjusted D-Dimer level. D-dimer > 1000 µg/l led to an unacceptable failure rate to 8.1% (4.4-14.5%). The best performances of the revised Geneva and Wells scores were obtained using the age-adjusted D-Dimer level. They had the same failure rate of 1.0% (0.2-5.3%) for efficiency of 16.8% (14.7-19.1%), and 16.9% (14.8-19.2%) respectively. The developed COVID-19 PE prediction model had an AUC of 0.609 (0.594-0.623) with an efficiency of 20.5% (18.4-22.8%) when its failure was set to 0.8%. CONCLUSIONS: The strategy to safely exclude PE in COVID-19 outpatients should not differ from that used in non-COVID-19 patients. The added value of the COVID-19 PE prediction model is minor. KEY POINTS: • D-dimer level remains the most important predictor of pulmonary embolism in COVID-19 patients. • The AUCs of the revised Geneva and Wells scores using an age-adjusted D-dimer threshold were 0.587 (95%CI, 0.572 to 0.603) and 0.588 (95%CI, 0.572 to 0.603). • The AUC of COVID-19-specific strategy to rule out pulmonary embolism ranged from 0.513 (95%CI: 0.503 to 0.522) to 0.609 (95%CI: 0.594 to 0.623).

D-dimer testing in clinical practice in the era of COVID-19.

D-dimer is a fragment of crosslinked fibrin resulting from plasmin cleavage of fibrin clots and hence an indirect biomarker of the hemostatic system activation. Early in the coronavirus disease 2019 (COVID-19) pandemic, several studies described coagulation disorders in affected patients, including high D-dimer levels. Consequently, D-dimer has been widely used in not-yet-approved indications. Ruling out pulmonary embolism and deep vein thrombosis in patients with low or intermediate clinical suspicion is the main application of D-dimer. D-dimer is also used to estimate the risk of venous thromboembolism recurrence and is included in the ISTH algorithm for the diagnosis of disseminated intravascular coagulation. Finally, numerous studies identified high D-dimer levels as a biomarker of poor prognosis in hospitalized patients with COVID-19. This report focuses on validated applications of D-dimer testing in patients with and without COVID-19.

Platelet activation and coronavirus disease 2019 mortality: Insights from coagulopathy, antiplatelet therapy and inflammation.

BACKGROUND: Coronavirus disease 2019 (COVID-19) is associated with an inflammatory cytokine burst and a prothrombotic coagulopathy. Platelets may contribute to microthrombosis, and constitute a therapeutic target in COVID-19 therapy. AIM: To assess if platelet activation influences mortality in COVID-19. METHODS: We explored two cohorts of patients with COVID-19. Cohort A included 208 ambulatory and hospitalized patients with varying clinical severities and non-COVID patients as controls, in whom plasma concentrations of the soluble platelet activation biomarkers CD40 ligand (sCD40L) and P-selectin (sP-sel) were quantified within the first 48hours following hospitalization. Cohort B was a multicentre cohort of 2878 patients initially admitted to a medical ward. In both cohorts, the primary outcome was in-hospital mortality. RESULTS: In cohort A, median circulating concentrations of sCD40L and sP-sel were only increased in the 89 critical patients compared with non-COVID controls: sP-sel 40,059 (interquartile range 26,876-54,678)pg/mL; sCD40L 1914 (interquartile range 1410-2367)pg/mL (P<0.001 for both). A strong association existed between sP-sel concentration and in-hospital mortality (Kaplan-Meier log-rank P=0.004). However, in a Cox model considering biomarkers of immunothrombosis, sP-sel was no longer associated with mortality, in contrast to coagulopathy evaluated with D-dimer concentration (hazard ratio 4.86, 95% confidence interval 1.64-12.50). Moreover, in cohort B, a Cox model adjusted for co-morbidities suggested that prehospitalization antiplatelet agents had no significant impact on in-hospital mortality (hazard ratio 1.05, 95% CI 0.80-1.37; P=0.73). CONCLUSIONS: Although we observed an association between excessive biomarkers of platelet activation and in-hospital mortality, our findings rather suggest that coagulopathy is more central in driving disease progression, which may explain why prehospitalization antiplatelet drugs were not a protective factor against mortality in our multicentre cohort.

Increased Circulating CD62E+ Endothelial Extracellular Vesicles Predict Severity and in- Hospital Mortality of COVID-19 Patients.

COVID-19 and infectious diseases have been included in strategic development goals (SDG) of United Nations (UN). Severe form of COVID-19 has been described as an endothelial disease. In order to better evaluate Covid-19 endotheliopathy, we characterized several subsets of circulating endothelial extracellular vesicles (EVs) at hospital admission among a cohort of 60 patients whose severity of COVID-19 was classified at the time of inclusion. Degree of COVID-19 severity was determined upon inclusion and categorized as moderate to severe in 40 patients and critical in 20 patients. We measured citrated plasma EVs expressing endothelial membrane markers. Endothelial EVs were defined as harboring VE-cadherin (CD144+), PECAM-1 (CD31 + CD41-) or E-selectin (CD62E+). An increase in CD62E + EV levels on admission to the hospital was significantly associated with critical disease. Moreover, Kaplan-Meier survival curves for CD62E + EV level showed that level ≥ 88,053 EVs/µL at admission was a significant predictor of in hospital mortality (p = 0.004). Moreover, CD62E + EV level ≥ 88,053 EV/µL was significantly associated with higher in-hospital mortality (OR 6.98, 95% CI 2.1-26.4, p = 0.002) in a univariate logistic regression model, while after adjustment to BMI CD62E + EV level ≥ 88,053 EV/µL was always significantly associated with higher in-hospital mortality (OR 5.1, 95% CI 1.4-20.0, p = 0.01). The present findings highlight the potential interest of detecting EVs expressing E-selectin (CD62) to discriminate Covid-19 patients at the time of hospital admission and identify individuals with higher risk of fatal outcome.

Respiratory recovery trajectories after severe-to-critical COVID-19: a 1-year prospective multicentre study.

BACKGROUND: Survivors of severe-to-critical coronavirus disease 2019 (COVID-19) may have functional impairment, radiological sequelae and persistent symptoms requiring prolonged follow-up. This pragmatic study aimed to describe their clinical follow-up and determine their respiratory recovery trajectories, and the factors that could influence them and their health-related quality of life. METHODS: Adults hospitalised for severe-to-critical COVID-19 were evaluated at 3 months and up to 12 months post-hospital discharge in this prospective, multicentre, cohort study. RESULTS: Among 485 enrolled participants, 293 (60%) were reassessed at 6 months and 163 (35%) at 12 months; 89 (51%) and 47 (27%) of the 173 participants initially managed with standard oxygen were reassessed at 6 and 12 months, respectively. At 3 months, 34%, 70% and 56% of the participants had a restrictive lung defect, impaired diffusing capacity of the lung for carbon monoxide (D LCO) and significant radiological sequelae, respectively. During extended follow-up, both D LCO and forced vital capacity percentage predicted increased by means of +4 points at 6 months and +6 points at 12 months. Sex, body mass index, chronic respiratory disease, immunosuppression, pneumonia extent or corticosteroid use during acute COVID-19 and prolonged invasive mechanical ventilation (IMV) were associated with D LCO at 3 months, but not its trajectory thereafter. Among 475 (98%) patients with at least one chest computed tomography scan during follow-up, 196 (41%) had significant sequelae on their last images. CONCLUSIONS: Although pulmonary function and radiological abnormalities improved up to 1 year post-acute COVID-19, high percentages of severe-to-critical disease survivors, including a notable proportion of those managed with standard oxygen, had significant lung sequelae and residual symptoms justifying prolonged follow-up.

Imbalance between alpha-1-antitrypsin and interleukin 6 is associated with in-hospital mortality and thrombosis during COVID-19.

Thrombosis is a hallmark of severe COVID-19. Alpha-1-antitrypsin (AAT), an inflammation-inducible serpin with anti-inflammatory, tissue protective and anticoagulant properties may be involved in severe COVID-19 pathophysiology including thrombosis onset. In this study, we examined AAT ability to predict occurrence of thrombosis and in-hospital mortality during COVID-19. To do so, we performed a monocentric cross-sectional study of 137 hospitalized patients with COVID-19 of whom 56 (41%) were critically ill and 33 (22.4%) suffered from thrombosis during hospitalization. We measured AAT and IL-6 plasma levels in all patients and phenotyped AAT in a subset of patients with or without thrombosis paired for age, sex and COVID-19 severity. We observed that AAT levels at admission were higher in both non-survivors and thrombosis patients than in survivors and non-thrombosis patients. AAT: IL-6 ratio was lower in non-survivors and thrombosis patients. In a logistic regression multivariable analysis model adjusted on age, BMI and D-dimer levels, a higher AAT: IL-6 was a protective factor of both in-hospital mortality (Odds ratio, OR: 0.07 95%CI [0.02-0.25], p < 0.001) and thrombosis (OR 0.36 95%CI [0.14-0.82], p = 0.02). AAT phenotyping did not show a higher proportion of AAT abnormal variants in thrombosis patients.Our findings suggest an insufficient production of AAT regarding inflammation intensity during severe COVID-19. AAT appeared as a powerful predictive marker of severity, mortality and thrombosis mirroring the imbalance between harmful inflammation and protective counter-balancing mechanism in COVID-19. Restoring the balance between AAT and inflammation could offer therapeutic opportunities in severe COVID-19.

Dynamics of circulating calprotectin accurately predict the outcome of moderate COVID-19 patients.

BACKGROUND: Severe COVID-19 is associated with a high circulating level of calprotectin, the S100A8/S100A9 alarmin heterodimer. Baseline calprotectin amount measured in peripheral blood at diagnosis correlates with disease severity. The optimal use of this biomarker along COVID-19 course remains to be delineated. METHODS: We focused on patients with a WHO-defined moderate COVID-19 requiring hospitalization in a medical ward. We collected plasma and serum from three independent cohorts (N = 626 patients) and measured calprotectin amount at admission. We performed longitudinal measures of calprotectin in 457 of these patients (1461 samples) and used a joint latent class mixture model in which classes were defined by age, body mass index and comorbidities to identify calprotectin trajectories predicting the risk of transfer into an intensive care unit or death. FINDINGS: After adjustment for age, sex, body mass index and comorbidities, the predictive value of baseline calprotectin in patients with moderate COVID19 could be refined by serial monitoring of the biomarker. We discriminated three calprotectin trajectories associated with low, moderate, and high risk of poor outcome, and we designed an algorithm available as online software (https://calpla.gustaveroussy.fr:8443/) to monitor the probability of a poor outcome in individual patients with moderate COVID-19. INTERPRETATION: These results emphasize the clinical interest of serial monitoring of calprotectin amount in the peripheral blood to anticipate the risk of poor outcomes in patients with moderate COVID-19 hospitalized in a standard care unit. FUNDING: The study received support (research grants) from ThermoFisher immunodiagnostics (France) and Gustave Roussy Foundation.

Adjusting D-dimer to Lung Disease Extent to Exclude Pulmonary Embolism in COVID-19 Patients (Co-LEAD).

OBJECTIVE: D-dimer measurement is a safe tool to exclude pulmonary embolism (PE), but its specificity decreases in coronavirus disease 2019 (COVID-19) patients. Our aim was to derive a new algorithm with a specific D-dimer threshold for COVID-19 patients. METHODS: We conducted a French multicenter, retrospective cohort study among 774 COVID-19 patients with suspected PE. D-dimer threshold adjusted to extent of lung damage found on computed tomography (CT) was derived in a patient set (n = 337), and its safety assessed in an independent validation set (n = 337). RESULTS: According to receiver operating characteristic curves, in the derivation set, D-dimer safely excluded PE, with one false negative, when using a 900 ng/mL threshold when lung damage extent was <50% and 1,700 ng/mL when lung damage extent was ≥50%. In the derivation set, the algorithm sensitivity was 98.2% (95% confidence interval [CI]: 94.7-100.0) and its specificity 28.4% (95% CI: 24.1-32.3). The negative likelihood ratio (NLR) was 0.06 (95% CI: 0.01-0.44) and the area under the curve (AUC) was 0.63 (95% CI: 0.60-0.67). In the validation set, sensitivity and specificity were 96.7% (95% CI: 88.7-99.6) and 39.2% (95% CI: 32.2-46.1), respectively. The NLR was 0.08 (95% CI; 0.02-0.33), and the AUC did not differ from that of the derivation set (0.68, 95% CI: 0.64-0.72, p = 0.097). Using the Co-LEAD algorithm, 76 among 250 (30.4%) COVID-19 patients with suspected PE could have been managed without CT pulmonary angiography (CTPA) and 88 patients would have required two CTs. CONCLUSION: The Co-LEAD algorithm could safely exclude PE, and could reduce the use of CTPA in COVID-19 patients. Further prospective studies need to validate this strategy.

What level of D-dimers can safely exclude pulmonary embolism in COVID-19 patients presenting to the emergency department?

OBJECTIVES: To identify which level of D-dimer would allow the safe exclusion of pulmonary embolism (PE) in COVID-19 patients presenting to the emergency department (ED). METHODS: This retrospective study was conducted on the COVID database of Assistance Publique - Hôpitaux de Paris (AP-HP). COVID-19 patients who presented at the ED of AP-HP hospitals between March 1 and May 15, 2020, and had CTPA following D-dimer dosage within 48h of presentation were included. The D-dimer sensitivity, specificity, and positive and negative predictive values were calculated for different D-dimer thresholds, as well as the false-negative and failure rates, and the number of CTPAs potentially avoided. RESULTS: A total of 781 patients (mean age 62.0 years, 53.8% men) with positive RT-PCR for SARS-Cov-2 were included and 60 of them (7.7%) had CTPA-confirmed PE. Their median D-dimer level was significantly higher than that of patients without PE (4,013 vs 1,198 ng·mL-1, p < 0.001). Using 500 ng·mL-1, or an age-adjusted cut-off for patients > 50 years, the sensitivity and the NPV were above 90%. With these thresholds, 17.1% and 31.5% of CTPAs could have been avoided, respectively. Four of the 178 patients who had a D-dimer below the age-adjusted cutoff had PE, leading to an acceptable failure rate of 2.2%. Using higher D-dimer cut-offs could have avoided more CTPAs, but would have lowered the sensitivity and increased the failure rate. CONCLUSION: The same D-Dimer thresholds as those validated in non-COVID outpatients should be used to safely rule out PE. KEY POINTS: • The median D-dimer level was significantly higher in COVID-19 patients with PE as compared to those without PE (4,013 ng·mL-1 vs 1,198 ng·mL-1 respectively, p < 0.001). • Using 500 ng·mL-1, or an age-adjusted D-dimer cut-off to exclude pulmonary embolism, the sensitivity and negative predictive value were above 90%. • Higher cut-offs would lead to a reduction in the sensitivity below 85% and an increase in the failure rate, especially for patients under 50 years.

Intermediate- vs. Standard-Dose Prophylactic Anticoagulation in Patients With COVID-19 Admitted in Medical Ward: A Propensity Score-Matched Cohort Study.

Background: Microthrombosis and large-vessel thrombosis are the main triggers of COVID-19 worsening. The optimal anticoagulant regimen in COVID-19 patients hospitalized in medical wards remains unknown. Objectives: To evaluate the effects of intermediate-dose vs. standard-dose prophylactic anticoagulation (AC) among patients with COVID-19 hospitalized in medical wards. Methods and results: We used a large French multicentric retrospective study enrolling 2,878 COVID-19 patients hospitalized in medical wards. After exclusion of patients who had an AC treatment before hospitalization, we generated a propensity-score-matched cohort of patients who were treated with intermediate-dose or standard-dose prophylactic AC between February 26 and April 20, 2020 (intermediate-dose, n = 261; standard-dose prophylactic anticoagulation, n = 763). The primary outcome of the study was in-hospital mortality; this occurred in 23 of 261 (8.8%) patients in the intermediate-dose group and 74 of 783 (9.4%) patients in the standard-dose prophylactic AC group (p = 0.85); while time to death was also the same in both the treatment groups (11.5 and 11.6 days, respectively, p = 0.17). We did not observe any difference regarding venous and arterial thrombotic events between the intermediate dose and standard dose, respectively (venous thrombotic events: 2.3 vs. 2.4%, p=0.99; arterial thrombotic events: 2.7 vs. 1.2%, p = 0.25). The 30-day Kaplan-Meier curves for in-hospital mortality demonstrate no statistically significant difference in in-hospital mortality (HR: 0.99 (0.63-1.60); p = 0.99). Moreover, we found that no particular subgroup was associated with a significant reduction in in-hospital mortality. Conclusion: Among COVID-19 patients hospitalized in medical wards, intermediate-dose prophylactic AC compared with standard-dose prophylactic AC did not result in a significant difference in in-hospital mortality.

Cardiometabolic Disorders and the Risk of Critical COVID-19 as Compared to Influenza Pneumonia.

We aimed to compare the influence of cardiometabolic disorders on the incidence of severe COVID-19 vs. non-COVID pneumonia. We included all consecutive patients admitted with SARS-CoV-2-positive pneumonia between 12 March 2020 and 1 April 2020 and compared them to patients with influenza pneumonia hospitalized between December 2017 and December 2019 at the same tertiary hospital in Paris. Patients with COVID-19 were significantly younger and more frequently male. In the analysis adjusted for age and sex, patients with COVID-19 were more likely to be obese (adjOR: 2.25; 95% CI 1.24-4.09; p = 0.0076) and receive diuretics (adjOR: 2.13; 95% CI 1.12-4.03; p = 0.021) but were less likely to be smokers (adjOR: 0.40; 95% CI 0.24-0.64; p = 0.0002), have COPD (adjOR: 0.25; 95% CI 0.11-0.56; p = 0.0008), or have a previous or active cancer diagnosis (adjOR: 0.54, 95% CI 0.32-0.91; p = 0.020). The rate of ICU admission was significantly higher in patients with COVID-19 (32.4% vs. 5.2% p < 0.0001). Obesity was significantly associated with the risk of direct ICU admission in patients with COVID-19 but not in patients with influenza pneumonia. Likewise, pre-existing hypertension was significantly associated with mortality in patients with COVID-19 but not in patients with influenza pneumonia. Cardiometabolic disorders differentially influenced the risk of presenting with severe COVID-19 or influenza pneumonia.

Lupus Anticoagulant Single Positivity During the Acute Phase of COVID-19 Is Not Associated With Venous Thromboembolism or In-Hospital Mortality.

OBJECTIVE: The clinical relevance of antiphospholipid antibodies (aPLs) in COVID-19 is controversial. This study was undertaken to investigate the prevalence and prognostic value of conventional and nonconventional aPLs in patients with COVID-19. METHODS: This was a multicenter, prospective observational study in a French cohort of patients hospitalized with suspected COVID-19. RESULTS: Two hundred forty-nine patients were hospitalized with suspected COVID-19, in whom COVID-19 was confirmed in 154 and not confirmed in 95. We found a significant increase in lupus anticoagulant (LAC) positivity among patients with COVID-19 compared to patients without COVID-19 (60.9% versus 23.7%; P < 0.001), while prevalence of conventional aPLs (IgG and IgM anti-ß2 -glycoprotein I and IgG and IgM anticardiolipin isotypes) and nonconventional aPLs (IgA isotype of anticardiolipin, IgA isotype of anti-ß2 -glycoprotein I, IgG and IgM isotypes of anti-phosphatidylserine/prothrombin, and IgG and IgM isotypes of antiprothrombin) was low in both groups. Patients with COVID-19 who were positive for LAC, as compared to patients with COVID-19 who were negative for LAC, had higher levels of fibrinogen (median 6.0 gm/liter [interquartile range 5.0-7.0] versus 5.3 gm/liter [interquartile range 4.3-6.4]; P = 0.028) and C-reactive protein (CRP) (median 115.5 mg/liter [interquartile range 66.0-204.8] versus 91.8 mg/liter [interquartile range 27.0-155.1]; P = 0.019). Univariate analysis did not show any association between LAC positivity and higher risks of venous thromboembolism (VTE) (odds ratio 1.02 [95% confidence interval 0.44-2.43], P = 0.95) or in-hospital mortality (odds ratio 1.80 [95% confidence interval 0.70-5.05], P = 0.24). With and without adjustment for CRP level, age, and sex, Kaplan-Meier survival curves according to LAC positivity confirmed the absence of an association with VTE or in-hospital mortality (unadjusted P = 0.64 and P = 0.26, respectively; adjusted hazard ratio 1.13 [95% confidence interval 0.48-2.60] and 1.80 [95% confidence interval 0.67-5.01], respectively). CONCLUSION: Patients with COVID-19 have an increased prevalence of LAC positivity associated with biologic markers of inflammation. However, LAC positivity at the time of hospital admission is not associated with VTE risk and/or in-hospital mortality.

Deterioration of vaccine-induced immune thrombotic thrombocytopenia treated by heparin and platelet transfusion: Insight from functional cytometry and serotonin release assay.

We report a case of a 62-year-old man who developed cerebral venous sinus thrombosis with subarachnoid hemorrhage and concomitant thrombocytopenia, which occurred 13 days after ChAdOx1 nCov-19 injection. The patient died in the intensive care unit after heparin infusion and platelet transfusion. The key clinical purpose of this case report is to better understand how to confirm vaccine-induced immune thrombotic thrombocytopenia (VITT). VITT diagnosis was made using 14C-serotonin release and flow cytometry evaluating activation and platelet microvesicles on washed platelets. Four control patients were examined: a patient with heparin-induced thrombocytopenia (HIT), two patients with thrombotic events without thrombocytopenia after ChAdOx1 nCov-19 or BNT162b2, and a patient with suspected HIT and an excluded diagnosis. We evidenced in the VITT case a high level of IgG anti-platelet factor 4-heparin antibodies associated with a high level of platelet activation in the absence of heparin. Conversely, the functional assays were negative in the patients with thrombosis without thrombocytopenia.

COVID-19 is a systemic vascular hemopathy: insight for mechanistic and clinical aspects.

Coronavirus disease 2019 (COVID-19) caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is presenting as a systemic disease associated with vascular inflammation and endothelial injury. Severe forms of SARS-CoV-2 infection induce acute respiratory distress syndrome (ARDS) and there is still an ongoing debate on whether COVID-19 ARDS and its perfusion defect differs from ARDS induced by other causes. Beside pro-inflammatory cytokines (such as interleukin-1 ß [IL-1ß] or IL-6), several main pathological phenomena have been seen because of endothelial cell (EC) dysfunction: hypercoagulation reflected by fibrin degradation products called D-dimers, micro- and macrothrombosis and pathological angiogenesis. Direct endothelial infection by SARS-CoV-2 is not likely to occur and ACE-2 expression by EC is a matter of debate. Indeed, endothelial damage reported in severely ill patients with COVID-19 could be more likely secondary to infection of neighboring cells and/or a consequence of inflammation. Endotheliopathy could give rise to hypercoagulation by alteration in the levels of different factors such as von Willebrand factor. Other than thrombotic events, pathological angiogenesis is among the recent findings. Overexpression of different proangiogenic factors such as vascular endothelial growth factor (VEGF), basic fibroblast growth factor (FGF-2) or placental growth factors (PlGF) have been found in plasma or lung biopsies of COVID-19 patients. Finally, SARS-CoV-2 infection induces an emergency myelopoiesis associated to deregulated immunity and mobilization of endothelial progenitor cells, leading to features of acquired hematological malignancies or cardiovascular disease, which are discussed in this review. Altogether, this review will try to elucidate the pathophysiology of thrombotic complications, pathological angiogenesis and EC dysfunction, allowing better insight in new targets and antithrombotic protocols to better address vascular system dysfunction. Since treating SARS-CoV-2 infection and its potential long-term effects involves targeting the vascular compartment and/or mobilization of immature immune cells, we propose to define COVID-19 and its complications as a systemic vascular acquired hemopathy.

Von Willebrand factor collagen-binding capacity predicts in-hospital mortality in COVID-19 patients: insight from VWF/ADAMTS13 ratio imbalance.

BACKGROUND: Microthrombosis is a hallmark of COVID-19. We previously described von willebrand factor (VWF) and their high molecular weight multimers (HMWMs) as potential trigger of microthrombosis. OBJECTIVES: Investigate VWF activity with collagen-binding assay and ADAMTS13 in COVID-19. METHODS AND RESULTS: Our study enrolled 77 hospitalized COVID-19 patients including 37 suffering from a non-critical form and 40 with critical form. Plasma levels of VWF collagen-binding ability (VWF:CB) and ADAMTS13 activity (ADAMTS13:Act) were measured in the first 48 hours following admission. VWF:CB was increased in critical (631% IQR [460-704]) patients compared to non-critical patients (259% [235-330], p < 0.005). VWF:CB was significantly associated (r = 0.564, p < 0.001) with HMWMs. Moreover, median ADAMTS13:Act was lower in critical (64.8 IU/dL IQR 50.0-77.7) than non-critical patients (85.0 IU/dL IQR 75.8-94.7, p < 0.001), even if no patients displayed majors deficits. VWF:Ag-to-ADAMTS13:Act ratio was highly associated with VWF:CB (r = 0.916, p < 0.001). Moreover, VWF:CB level was highly predictive of COVID-19 in-hospital mortality as shown by the ROC curve analysis (AUC = 0.92, p < 0.0001) in which we identified a VWF:CB cut-off of 446% as providing the best predictor sensitivity-specificity balance. We confirmed this cut-off thanks to a Kaplan-Meier estimator analysis (log-rank p < 0.001) and a Cox-proportional Hazard model (HR = 49.1, 95% CI 1.81-1328.2, p = 0.021) adjusted on, BMI, C-reactive protein, and D-dimer levels. CONCLUSION: VWF:CB levels could summarize both VWF increased levels and hyper-reactivity subsequent to ADAMTS13 overflow and, therefore, be a valuable and easy to perform clinical biomarker of microthrombosis and COVID-19 severity.