Delayed Plasma Clot Lysis in Adult Patients with Primary Immune Thrombocytopenia (ITP)

Introduction: Primary immune thrombocytopenia (ITP) is an orphan disease characterized by very low platelet counts. Patients have heterogeneous bleeding phenotypes, which are not only determined by platelet counts, also a paradoxically increased thrombotic risk has been observed. Aim: To investigate, whether the fibrinolysis inhibitors plasminogen activator inhibitor-1 (PAI-1) and α2-antiplasmin are associated with impaired plasma clot lysis in primary ITP patients in comparison to non-immunologic thrombocytopenic controls (TPC) and healthy controls (HC). Furthermore, associations with bleeding severity and previous thrombotic events were investigated. Methods: Patients from the Vienna ITP biobank (EC 1843/2016), a multi-centric study including adult patients with primary ITP were investigated and compared to age- and sex-matched control groups: TPC with thrombocytopenia after chemotherapy and HC. Informed consent was obtained from all individuals before study inclusion. A clot formation and lysis assay (CLA) was performed according to the recommendations of the ISTH SSC. Platelet poor plasma samples were measured in duplicates for each patient and control. PAI-1 (PAI-1 Actibind ELISA, Technoclone, Vienna, Austria) and α2-antiplasmin by the chromogenic STA Stachrom antiplasmin assay (Diagnostic Stago, Asnieres, France) were measured. Bleeding severity was measured using the ITP-specific ITP-ISTH BAT (Rodeghiero et al. 2013). Results: In total, 37 primary ITP patients, 18 TPC and 156 healthy controls were analyzed (Table 1). Primary ITP patients had a higher BMI than HC. Bleeding severity was higher and more ITP patients had a thrombosis history compared to HC, whereas there was no difference in comparison to TPC. PAI-1 activity was highest in ITP patients, with a statistically significant difference in comparison to HC. α2-antiplasmin activity was higher in ITP patients than in TPC, whereas there was no difference in comparison to HC. After adjustment for sex, age, BMI and fibrinogen, primary ITP patients had a reduced clot formation rate (V max) and significantly delayed plasma clot lysis compared to TPC and HC (Table 2). Also, the lag phase and time to peak absorbance (TTP) were prolonged with a significant difference in comparison to HC. To investigate outliers of PAI-1 and α2-antiplasmin, we calculated cut-offs at the 75 th percentile of healthy controls (PAI-1: ≥ 3.1 U/mL, α2-antiplasmin: ≥ 107.0 %). 14 (37.8 %) ITP patients had PAI-1 levels and 10 (27.0 %) ITP patients had α2-antiplasmin activity above the cut-off. ITP patients with high PAI-1 levels had mildly delayed clot lysis in comparison to those below with a significantly lower maximal lysis rate (mLR). ITP patients with α2-antiplasmin activity above the cut-off had a significantly shorter lag phase, faster V max and shorter TTP than patients below the cut-off, whereas there was no difference in clot lysis. No differences between ITP patients above or below the respective cut-offs of PAI-1 and α2-antiplasmin regarding their bleeding severity and thrombosis incidence were observed (Table 3). Conclusion: Primary ITP patients have a tendency towards increased PAI-1 activity, which is associated with considerably delayed plasma clot lysis. Albeit an association with the bleeding score could not be identified, this impaired lysis could be seen as a counter-regulation and at least contribute to the relatively mild bleeding tendency in patients with ITP. Figure 1 Figure 1. Disclosures Pabinger: CSL Behring: Consultancy, Honoraria, Research Funding; NovoNordisk: Consultancy, Research Funding; Bayer: Consultancy, Honoraria; Takeda: Consultancy, Honoraria; Daiichi Sanchyo: Consultancy, Honoraria; Alexion: Consultancy, Honoraria; Novartis: Consultancy, Honoraria; Amgen: Consultancy, Honoraria; Pfizer: Consultancy, Honoraria.

Epidemiology of Bleeding in Critically Ill Children

Objective: Bleeding can be a severe complication of critical illness, but its true epidemiologic impact on children has seldom been studied. Our objective is to describe the epidemiology of bleeding in critically ill children, using a validated clinical tool, as well as the hemostatic interventions and clinical outcomes associated with bleeding.Design: Prospective observational cohort study.Setting: Tertiary pediatric critical care unitPatients: All consecutive patients (1 month to 18 years of age) admitted to a tertiary pediatric critical care unitMeasurements and Main Results: Bleeding events were categorized as minimal, moderate, severe, or fatal, according to the Bleeding Assessment Scale in Critically Ill Children. We collected demographics and severity at admission, as evaluated by the Pediatric Index of Mortality. We used regression models to compare the severity of bleeding with outcomes adjusting for age, surgery, and severity. Over 12 months, 902 critically ill patients were enrolled. The median age was 64 months (IQR 17; 159), the median admission predicted risk of mortality was 0.5% (IQR 0.2; 1.4), and 24% were post-surgical. Eighteen percent of patients experienced at least one bleeding event. The highest severity of bleeding was minimal for 7.9% of patients, moderate for 5.8%, severe for 3.8%, and fatal for 0.1%. Adjusting for age, severity at admission, medical diagnosis, type of surgery, and duration of surgery, bleeding severity was independently associated with fewer ventilator-free days (p < 0.001) and fewer PICU-free days (p < 0.001). Adjusting for the same variables, bleeding severity was independently associated with an increased risk of mortality (adjusted odds ratio for each bleeding category 2.4, 95% CI 1.5; 3.7, p < 0.001).Conclusion: Our data indicate bleeding occurs in nearly one-fifth of all critically ill children, and that higher severity of bleeding was independently associated with worse clinical outcome. Further multicenter studies are required to better understand the impact of bleeding in critically ill children.

Fully automated detection and segmentation of intracranial aneurysms in subarachnoid hemorrhage on CTA using deep learning

In aneurysmal subarachnoid hemorrhage (aSAH), accurate diagnosis of aneurysm is essential for subsequent treatment to prevent rebleeding. However, aneurysm detection proves to be challenging and time-consuming. The purpose of this study was to develop and evaluate a deep learning model (DLM) to automatically detect and segment aneurysms in patients with aSAH on computed tomography angiography. In this retrospective single-center study, three different DLMs were trained on 68 patients with 79 aneurysms treated for aSAH (2016–2017) using five-fold-cross-validation. Their outputs were combined to a single DLM via ensemble-learning. The DLM was evaluated on an independent test set consisting of 185 patients with 215 aneurysms (2010–2015). Independent manual segmentations of aneurysms in a 3D voxel-wise manner by two readers (neurosurgeon, radiologist) provided the reference standard. For aneurysms > 30 mm3 (mean diameter of ~ 4 mm) on the test set, the DLM provided a detection sensitivity of 87% with false positives (FPs)/scan of 0.42. Automatic segmentations achieved a median dice similarity coefficient (DSC) of 0.80 compared to the reference standard. Aneurysm location (anterior vs. posterior circulation; P = .07) and bleeding severity (Fisher grade ≤ 3 vs. 4; P = .33) did not impede detection sensitivity or segmentation performance. For aneurysms > 100 mm3 (mean diameter of ~ 6 mm), a sensitivity of 96% with DSC of 0.87 and FPs/scan of 0.14 were obtained. In the present study, we demonstrate that the proposed DLM detects and segments aneurysms > 30 mm3 in patients with aSAH with high sensitivity independent of cerebral circulation and bleeding severity while producing FP findings of less than one per scan. Hence, the DLM can potentially assist treating physicians in aSAH by providing automated detection and segmentations of aneurysms.

Association of ABO Blood Group with Bleeding Severity in Patients with Bleeding of Unknown Cause

Introduction: Antigens of the ABO blood group system have an impact on the hemostatic balance. The association of blood group non-O and thrombosis risk is well known. In patients with different bleeding manifestations, an overrepresentation of blood group O has been previously reported (Dentali et al, Semin.Thromb. Hemost, 2013). Nevertheless, the independent effect of the ABO blood group on bleeding severity, when considering VWF as a major contributing factor, has not yet been thoroughly investigated. Patients with bleeding of unknown cause (BUC) have a similar bleeding phenotype as patients with a diagnosis of an established bleeding disorder, but the causes underlying their bleeding tendency are currently unclear and might be multifactorial (Gebhart et al, Haemophilia, 2018). Thus, we investigated the prevalence of blood group O and its role as an independent risk factor for increased bleeding severity in a thoroughly characterized cohort of patients with BUC. Methods: For this analysis, we selected all patients with normal results in the assessments of plasmatic coagulation and platelet function consecutively recruited between October 2009 and April 2019 within the Vienna bleeding biobank study (Figure 1; Gebhart et al, Haemophilia, 2018). After informed consent, all patients underwent a structured interview on their previous medical and bleeding history including the assessment of the bleeding severity with the Vicenza bleeding assessment tool (BAT). Biomaterial was processed and stored according to standard operating procedures at the Biobank facility (http://www.biobank.at/). A thorough hemostatic laboratory assessment and measurements of thrombin generation, plasma clot properties, and rotational thromboelastometry (ROTEM), as well as platelet function tests (PFA-100, light transmission aggregometry) were performed. Data on the blood group distribution of 23,145 healthy first-time blood donors were provided by the Austrian Red Cross for comparison. Results: We observed an overrepresentation of blood group O in 199 out of 422 BUC patients (47.2%) compared to 8709 out of 23,145 healthy blood donors (37.6%), odds ratio for blood group O 1.48; 95% CI=1.22-1.79, p<0.001 (Table 1). Blood group O in comparison to non-blood group O was independently associated with an increased bleeding severity (least square mean [95% CI]: 6.2 [5.8-6.6] vs. 5.3 [4.9-5.7], p=0.006) and a higher number of bleeding symptoms (least square (LS) mean [95% CI] 3.5 [3.2-3.7] vs. 3.0 [2.8-3.2], p=0.016), after adjustment for sex, VWF:Ag, VWF:RCo and FVIII activity (Table 2). The prevalence of oral mucosal bleeding was significantly higher in blood group O than in patients with a non-O blood group (26.1% vs. 14.3%), even after adjustment for sex, VWF and FVIII, and multiple testing (p=0.013). When analyzing the influence of blood group O on tests of global hemostatic capacity, results indicated increased clot firmness and reduced lysis in blood group O patients. In ROTEM, the maximum clot firmness was higher (LS mean [95% CI]: 57.4 [56.5-58.3] vs. 55.8 [55.0-56.6] mm, p<0.05) and the maximal lysis lower (LS mean [95% CI]: 13.3 [12.5-14.1] vs. 15.1 [14.4-15.9] %, p<0.05) in patients with blood group O compared to non-O patients, after adjustment for sex, VWF and FVIII, and correction for multiple testing. Also in the analysis of plasma clot properties, the maximum clot absorbance was increased in patients with blood group O after adjustment for sex, VWF and FVIII (LS mean [95% CI]: 0.77 [0.74-0.79] vs 0.71 [0.69-0.74] OD, p<0.05), whereas there was no difference in plasma clot lysis. There was no difference in thrombin generation between BUC patients with blood group O and non-O. We could not identify any differences in platelet function, as assessed by the platelet function analyser-100 and light transmission aggregometry between patients with blood group O in comparison to non-O patients after adjustment for sex, VWF and FVIII, and correction for multiple testing. Conclusion : Blood group O is a risk factor for a more severe bleeding phenotype, especially oral mucosal bleeding, independent of VWF and FVIII levels in patients with BUC. Alterations in global hemostatic capacity in BUC patients with blood group O were identified, whereas platelet function was not different. Our data are important for a better understanding of underlying mechanisms of bleeding in BUC patients, which are most probably multifactorial. Disclosures Jilma: True North Therapeutics: Consultancy, Other: reimbursement for travel costs for scientific presentations; Bioverativ: Consultancy, Other: reimbursement for travel costs for scientific presentations.

Association of ABO blood group with bleeding severity in patients with bleeding of unknown cause

Blood group O has been associated with an increased bleeding tendency due to lower von Willebrand factor (VWF) and factor VIII (FVIII) levels. We explored whether blood group O is independently associated with bleeding severity in patients with mild-to-moderate bleeding of unknown cause (BUC) in the Vienna Bleeding Biobank cohort. Bleeding severity was recorded with the Vicenza bleeding score (BS). Blood group O was overrepresented in 422 patients with BUC compared with its presence in 23 145 healthy blood donors (47.2% vs 37.6%; odds ratio, 1.48; 95% confidence interval [CI], 1.22-1.79). The BS and the number of bleeding symptoms were significantly higher in patients with blood group O than in patients with non-O after adjustment for VWF and FVIII levels and sex (least-square [LS] means of BSs: 6.2; 95% CI, 5.8-6.6 vs 5.3; 4.9-5.7; and of number of symptoms: LS, 3.5; 95% CI, 3.2-3.7 vs 3.0; 2.8-3.2, respectively). Oral mucosal bleeding was more frequent in those with blood group O than in those with other blood types (group non-O; 26.1% vs 14.3%), independent of sex and VWF and FVIII levels, whereas other bleeding symptoms did not differ. Patients with blood group O had increased clot density in comparison with those with blood group non-O, as determined by rotational thromboelastometry and turbidimetric measurement of plasma clot formation. There were no differences in thrombin generation, clot lysis, or platelet function. Our data indicate that blood group O is a risk factor for increased bleeding and bleeding severity in patients with BUC, independent of VWF and FVIII levels.

Bleeding severity in patients with rare bleeding disorders: real-life data from the RBiN study

Patients with hereditary rare bleeding disorders (RBDs) present with diverse hemorrhagic symptoms. Correlation between factor activity levels and clinical bleeding severity is poor for most RBDs. Threshold factor activity levels have been previously described in relation to bleeding severity but have not yet been validated. The Rare Bleeding Disorders in the Netherlands (RBiN) study is a nationwide cross-sectional study of patients registered in all 6 Dutch Haemophilia Treatment Centers with a known RBD and who are age 1 to 99 years. Bleeding scores were determined, and laboratory and clinical data were extracted from patient files. In all, 263 patients were included, of whom 202 (77%) attended the scheduled study visit. The median International Society of Thrombosis and Haemostasis (ISTH) bleeding assessment tool (BAT) score was 9. Correlations between baseline factor activity levels and ISTH BAT scores were strong for deficiencies in factor II (FII) (r = –0.792) and FX (r = –0.838) and were moderate for deficiencies of fibrinogen (r = –0.683), FV (r = –0.623), FVII (r = –0.516), FXIII (r = –0.516), and α2-antiplasmin (r = –0.594). There was no correlation for FXI deficiency (r = –0.218). The RBD BAT identified more women (94% vs 83%) and children (100% vs 71%) with an RBD than the ISTH BAT did. Importantly, 48% of patients had more severe bleeding than predicted for their baseline factor activity level. In addition, 34% of patients were predicted to be asymptomatic, but they actually had grade 2 (31%) or 3 (3%) bleeding. Bleeding severity in patients with RBDs is more pronounced than previously anticipated. The previously determined threshold factor activity levels to ensure no (spontaneous) bleeding in patients with an RBD are inaccurate. This trial was registered at www.clinicaltrials.gov as #NCT03347591.