Introduction: The British Lung Foundation recommends specialist review of patients with acute PE but this is not consistent UK practice, nor included in NICE guidance. Aims and Objectives: Evaluation of the effectiveness of specialist review of all patients after 6 months' treatment for acute PE. Methods: All patients over a 5-year period underwent retrospective review to assess diagnostic accuracy, persistence of cardio-respiratory symptoms, concluding explanatory diagnoses and requirement for specialist pulmonary hypertension service intervention. Results: 995 patients were identified. The diagnosis of acute PE was concluded as incorrect in 33 (3.3%) patients. In 24 (2%) patients with confirmed PE, additional diagnoses requiring significant management changes were identified. 49 (5%) patients were diagnosed with chronic thromboembolic disease and 37 (4%) were referred to the National Pulmonary Hypertension Service, Cambridge: 28 (3%) had pulmonary hypertension, 15 required pulmonary endarterectomy (plus patent foramen ovale closure in 2, and coronary artery bypass grafting in 2 patients). 12 patients required PH-specific pharmacotherapy and 7 died (1 prior to assessment, 1 following endarterectomy, 2 from right ventricular failure, 1 from pontine haemorrhage and 2 from unrelated comorbidities). Conclusions: 11% of patients had significant alterations made to their management. The incidence of chronic thromboembolic pulmonary hypertension was similar when compared to that identified in published reports from tertiary centres1,2. References: 1.Tapson VF et al. Proc Am Thorac Soc. 2006 Sep;3(7):564-7. 2.Guérin L et al. Thromb Haemost. 2014 Sep 2;112(3):598-605.

A single 1 g/kg dose of intravenous immunoglobulin is a safe and effective treatment for immune thrombocytopenia; results of the first HaemSTAR 'Flash-Mob' retrospective study incorporating 961 patients Key Messages 1 A one off 1 g/kg infusion of intravenous immunoglobulin (IVIg) may be as effective as two consecutive 1 g/kg doses. 2 This is the largest ever study of the efficacy of IVIg for immune thrombocytopenia (ITP).3 There is poor adherence to the 2016 NHS England guidelines on IVIg dosing.

Background: Low molecular-weight heparin (LMWH) is routinely administered to burn patients for thromboprophylaxis. Some studies have reported heparin resistance, yet the mechanism(s) and prevalence have not been systematically studied. We hypothesized that nucleosomes, composed of histone structures with associated DNA released from injured tissue and activated immune cells in the form of neutrophil extracellular traps (NETs or NETosis), neutralize LMWH resulting in suboptimal anticoagulation, assessed by reduction in anti-factor Xa activity. Methods: Blood was sampled from >15% total body surface area (TBSA) burn patients receiving LMWH on days 5, 10 and 14. Peak anti-factor Xa (AFXa) activity, anti-thrombin (ATIII) activity, cell-free DNA (cfDNA) levels and nucleosome levels were measured. Mixed effects regression was adjusted for multiple confounders, including injury severity and ATIII activity, and was used to test the association between nucleosomes and AFXa. Results: A total of 30 patients with severe burns were included. Mean TBSA 43% (SD 17). Twenty-three (77%) patients were affected by heparin resistance (defined by AFXa activity <0.2 IU/mL). Mean peak AFXa activity across samples was 0.18 IU/mL (SD 0.11). Mean ATIII was 81.9% activity (SD 20.4). Samples taken at higher LWMH doses were found to have significantly increased AFXa activity, though the effect was not observed at all doses, at 8000 IU no samples were heparin resistant. Nucleosome levels were negatively correlated with AFXa (r= -0.29, p= 0.050) consistent with the hypothesis. The final model, with peak AFXa as the response variable, was adjusted for nucleosome levels (p= 0.0453), ATIII activity (p= 0.0053), LMWH dose pre-sample (p= 0.0049), drug given (enoxaparin or tinzaparin) (p= 0.03), and other confounders including severity of injury, age, gender, time point of sample. Conclusions: Heparin resistance is a prevalent issue in severe burns. Nucleosome levels were increased post-burn, and showed an inverse association with AFXa consistent with the hypothesis that they may interfere with the anticoagulant effect of heparin in vivo and contribute to heparin resistance. Accurate monitoring of AFXa activity with appropriate therapy escalation plans are recommended with dose adjustment following severe burn injury.

The cornerstone of life-saving therapy in immune-mediated thrombotic thrombocytopenic purpura (iTTP) has been plasma exchange (PEX) combined with immunomodulatory strategies. Caplacizumab, a novel anti-von Willebrand factor nanobody trialed in 2 multi-center randomized controlled trials (RCTs) leading to European Union and US Food and Drug Administration approval, has been available in the United Kingdom (UK) through a patient access scheme. Data were collected retrospectively from 2018 to 2020 for 85 patients (4 children) receiving caplacizumab from 22 UK hospitals. Patient characteristics and outcomes in the real-world clinical setting were compared with caplacizumab trial end points and historical outcomes in the precaplacizumab era. Eighty-four of 85 patients received steroid and rituximab alongside PEX; 26% required intubation. Median time to platelet count normalization (3 days), duration of PEX (7 days), and hospital stay (12 days) were comparable with RCT data. Median duration of PEX and time from PEX initiation to platelet count normalization were favorable compared with historical outcomes (P <.05). Thrombotic thrombocytopenic purpura (TTP) recurred in 5 of 85 patients; all had persistent ADAMTS13 activity < 5 IU/dL. Of 31 adverse events in 26 patients, 17 of 31 (55%) were bleeding episodes, and 5 of 31 ( 16%) were thrombotic events ( 2 unrelated to caplacizumab); mortality was 6% ( 5/ 85), with no deaths attributed to caplacizumab. In 4 of 5 deaths, caplacizumab was introduced >48 hours after PEX initiation (3-21 days). This real-world evidence represents the first and largest series of TTP patients, including pediatric patients, receiving caplacizumab outside of clinical trials. Representative of true clinical practice, the findings provide valuable information for clinicians treating TTP globally.

Background The currently published population pharmacokinetic (PK) models used for PK-guided dosing in hemophilia patients are based on clinical trial data and usually not externally validated in clinical practice. The aim of this study was to validate a published model for recombinant factor VIII-Fc fusion protein (rFVIII-Fc) concentrate and to develop an enriched model using independently collected clinical data if required. Methods Clinical data from hemophilia A patients treated with rFVIII-Fc concentrate (Elocta) participating in the United Kingdom Extended Half-Life Outcomes Registry were collected. The predictive performance of the published model was assessed using mean percentage error (bias) and mean absolute percentage error (inaccuracy). An extended population PK model was developed using nonlinear mixed-effects modeling (NONMEM). Results A total of 43 hemophilia A patients (FVIII <= 2 IU/dL), aged 5 to 70 years, were included. The prior model was able to predict the collected 244 rFVIII-Fc levels without significant bias (-1.0%, 95% CI: -9.4 to 7.3%) and with acceptable accuracy (12.9%). However, clearance and central distribution volume were under predicted in patients <12 years, which was expected as this age group was not represented in the previous model population. An enriched population PK model was constructed, which was able to successfully characterize PK profiles of younger children. Conclusion We concluded that the existing rFVIII-Fc population PK model is valid for patients >= 12 years. However, it is not reliable in younger patients. Our alternative model, constructed from real world patient data including children, allows for better description of patients >= 5 years.