Clinical characteristics of patients with direct oral anticoagulant (DOAC) levels outside expected ranges:A retrospective chart study

Background: Routine monitoring direct oral anticoagulants (DOAC) is not recommended, yet DOAC levels are frequently measured in clinical practice. Interpretation of levels, especially those outside expected ranges, is challenging. Until now it's unclear which patients are at risk for these levels. Aim: Identify clinical characteristics of patients with DOAC levels outside expected ranges. Methods: Patients of 2 Dutch academic medical centers with a DOAC concentration measured between 2012 and 2019 were included. DOAC levels above upper limit peak and below lower limit trough ranges, based on DOAC registration trials, were assigned outside expected range. Differences between patients were evaluated using Chi-square, independent sample-T tests and multivariable logistic regression analysis. Results: Of 597 patients with DOAC measurement, 108 (18.1%) had levels outside expected ranges. Compared to patients with levels within range, patients with levels above range (n = 64) were older (71.1 vs. 60.6 years), more often had creatinine clearance <50 ml/min (32.8% vs. 13.9%). and used more often interacting (17.2% vs. 6.7%) and/or antiplatelet co-medication (25.0% vs. 13.1%). Patients with levels above (62.5%) and below range (61.4%) more often had atrial fibrillation as DOAC indication versus patients with levels within range (39.1%). Age (OR 1.046 [1.025–1.068]) was associated with levels above range, while dabigatran versus apixaban was associated with levels below range (OR 6.060 [1.836–19.996]). Conclusion: Particularly older aged patients with additional comorbidity and co-medication had DOAC levels outside expected ranges. Prospective studies are essential to investigate whether identification of patients with levels outside expected ranges is necessary to reduce the risk of clinically relevant adverse events

Platelet control of fibrin distribution and microelasticity in thrombus formation under flow

Objective—Platelet- and fibrin-dependent thrombus formation is regulated by blood flow and exposure of collagen and tissue factor. However, interactions between these blood-borne and vascular components are not well understood. Approach and Results—Here, we developed a method to assess whole-blood thrombus formation on microspots with defined amounts of collagen and tissue factor, allowing determination of the mechanical properties and intrathrombus composition. Confining the collagen content resulted in diminished platelet deposition and fibrin formation at high shear flow conditions, but this effect was compensated by a larger thrombus size and increased accumulation of fibrin in the luminal regions of the thrombi at the expense of the base regions. These thrombi were more dependent on tissue factor–triggered thrombin generation. Microforce nanoindentation analysis revealed a significantly increased microelasticity of thrombi with luminal-oriented fibrin. At a low shear rate, fibrin fibers tended to luminally cover the thrombi, again resulting in a higher microelasticity. Studies with blood from patients with distinct hemostatic insufficiencies indicated an impairment in the formation of a platelet–fibrin thrombus in the cases of dilutional coagulopathy, thrombocytopenia, Scott syndrome, and hemophilia B. Conclusions—Taken together, our data indicate that (1) thrombin increases the platelet thrombus volume; (2) tissue factor drives the formation of fibrin outside of the platelet thrombus; (3) limitation of platelet adhesion redirects fibrin from bottom to top of the thrombus; (4) a lower shear rate promotes thrombus coverage with fibrin; (5) the fibrin distribution pattern determines thrombus microelasticity; and (6) the thrombus-forming process is reduced in patients with diverse hemostatic defects

Applications of rotational thromboelastometry in heparin monitoring in critical COVID-19 disease: Observations in the Maastricht Intensive Care COVID cohort

Background: Critically ill COVID-19 patients are at risk for venous thromboembolism (VTE). Therefore, they receive thromboprophylaxis and, when appropriate, therapeutic unfractionated heparin (UFH) or low-molecular-weight heparin (LMWH). To monitor heparins in COVID-19 disease, whole-blood rotational thromboelastometry (ROTEM) may be a promising alternative to the aPTT and anti-Xa assays. Objective: To evaluate the ROTEM INTEM/HEPTEM ratios in mechanically ventilated COVID-19 patients treated with UFH and therapeutic LMWH. Material and methods: A subcohort of mechanically ventilated COVID-19 patients of the prospective Maastricht Intensive Care Covid (MaastrICCht) cohort was studied. Anti-Xa, aPTT, and ROTEM measurements following treatment with UFH or therapeutic dose of LMWH (nadroparin) were evaluated using uni- and multivariable linear regression analysis and receiver operating characteristics. Results: A total of 98 patients were included, of which 82 were treated with UFH and 16 with therapeutic LMWH. ROTEM-measured INTEM/HEPTEM CT ratio was higher in patients using UFH (1.4 [1.3–1.4]) compared to patients treated with LMWH (1.0 [1.0–1.1], p < 0.001). Both the aPTT and anti-Xa were associated with the CT ratio. However, the β-regression coefficient (95%CI) was significantly higher in patients on UFH (0.31 (0.001–0.62)) compared to therapeutic LMWH (0.09 (0.05–0.13)) for comparison with the anti-Xa assay. Furthermore, ROC analysis demonstrated an area under the curve for detecting UFH of 0.936(0.849–1.00), 0.851(0.702–1.000), and 0.645(0.465–0.826) for the CT ratio, aPTT, and anti-Xa, respectively. Conclusion: The ROTEM INTEM/HEPTEM CT ratio appears a promising tool to guide anticoagulant therapy in ICU patients with COVID-19 disease, but associations with clinical endpoints are currently lacking

Diagnostic high-throughput sequencing of 2396 patients with bleeding, thrombotic, and platelet disorders

A targeted high-throughput sequencing (HTS) panel test for clinical diagnostics requires careful consideration of the inclusion of appropriate diagnostic-grade genes, the ability to detect multiple types of genomic variation with high levels of analytic sensitivity and reproducibility, and variant interpretation by a multi-disciplinary team (MDT) in the context of the clinical phenotype. We have sequenced 2,396 index patients using the ThromboGenomics HTS panel test of diagnostic-grade genes known to harbour variants associated with rare bleeding, thrombotic or platelet disorders (BTPD). The molecular diagnostic rate was determined by the clinical phenotype, with an overall rate of 49.2% for all thrombotic, coagulation, platelet count and function disorder patients and a rate of 3.2% for patients with unexplained bleeding disorders characterized by normal hemostasis test results. The MDT classified 745 unique variants, including copy number and intronic variants, as Pathogenic, Likely Pathogenic or Variants of Uncertain Significance. Half (50.9%) of these variants are novel and 41 unique variants were identified in 7 genes recently found to be implicated in BTPD. Inspection of canonical hemostasis pathways identified 29 patients with evidence of oligogenic inheritance. A molecular diagnosis has been reported for 894 index patients providing evidence that introducing an HTS genetic test is a valuable addition to laboratory diagnostics in patients with a high likelihood of having an inherited BTPD

Assessment and determinants of whole blood and plasma fibrinolysis in patients with mild bleeding symptoms

Enhanced clot lysis is associated with bleeding, but assessment of lysis capacity remains difficult. The plasma turbidity lysis and whole blood tissue Plasminogen Activator-Rotational Thromboelastometry (tPA-ROTEM) assays estimate fibrinolysis under more physiological conditions than clinically used assays. We hypothesized that these assays could find signs of enhanced lysis capacity in patients who report bleeding symptoms, but are not diagnosed with bleeding disorders. We also aimed to gain insight in determinants of the results of these lysis assays. Data from 240 patients with and 95 patients without self-reported bleeding symptoms were obtained, who were included in a study that primarily aimed to assess prevalence of haemostaticabnormalities in preoperative patients. ROTEM and turbidity assays were performed with rtPA. Blood counts, fibrinolysis and coagulation factor activities were determined. Data were analysed using multivariable linear regression models. Remarkably, patients reporting bleeding symptoms showed signs of significantly impaired lysis capacity in the tPA-ROTEM, but not in the turbidity lysis assay. In these patients, the tPA-ROTEM results depended on FII, FXII, plasminogen, α2-antiplasmin, PAI-1 and TAFI levels. The turbidity lysis results were significantly influenced by fibrinogen, α2-antiplasmin, PAI-1 and TAFI. In conclusion, the tPA-ROTEM and the turbidity lysis assay could not detect enhanced fibrinolytic capacity in patients with bleeding symptoms. This suggests that these symptoms are not caused by enhanced fibrinolytic activity. As both assays were sensitive to important determinants of fibrinolysis they may be able to detect a fibrinolytic imbalance, but this needs to be validated in patients with known hypo- or hyperfibrinolytic disorders