Summary Background COVID-19 is an ongoing global pandemic. Changes in haematological characteristics in patients with COVID-19 are emerging as important features of the disease. We aimed to explore the haematological characteristics and related risk factors in patients with COVID-19. Methods This retrospective cohort study included patients with COVID-19 admitted to three designated sites of Wuhan Union Hospital (Wuhan, China). Demographic, clinical, laboratory, treatment, and outcome data were extracted from electronic medical records and compared between patients with moderate, severe, and critical disease (defined according to the diagnosis and treatment protocol for novel coronavirus pneumonia, trial version 7, published by the National Health Commission of China). We assessed the risk factors associated with critical illness and poor prognosis. Dynamic haematological and coagulation parameters were investigated with a linear mixed model, and coagulopathy screening with sepsis-induced coagulopathy and International Society of Thrombosis and Hemostasis overt disseminated intravascular coagulation scoring systems was applied. Findings Of 466 patients admitted to hospital from Jan 23 to Feb 23, 2020, 380 patients with COVID-19 were included in our study. The incidence of thrombocytopenia (platelet count <100 × 10 9 cells per L) in patients with critical disease (42 [49%] of 86) was significantly higher than in those with severe (20 [14%] of 145) or moderate (nine [6%] of 149) disease (p<0·0001). The numbers of lymphocytes and eosinophils were significantly lower in patients with critical disease than those with severe or moderate disease (p<0·0001), and prothrombin time, D-dimer, and fibrin degradation products significantly increased with increasing disease severity (p<0·0001). In multivariate analyses, death was associated with increased neutrophil to lymphocyte ratio (≥9·13; odds ratio [OR] 5·39 [95% CI 1·70–17·13], p=0·0042), thrombocytopenia (platelet count <100 × 10 9 per L; OR 8·33 [2·56–27·15], p=0·00045), prolonged prothrombin time (>16 s; OR 4·94 [1·50–16·25], p=0·0094), and increased D-dimer (>2 mg/L; OR 4·41 [1·06–18·30], p=0·041). Thrombotic and haemorrhagic events were common complications in patients who died (19 [35%] of 55). Sepsis-induced coagulopathy and International Society of Thrombosis and Hemostasis overt disseminated intravascular coagulation scores (assessed in 12 patients who survived and eight patients who died) increased over time in patients who died. The onset of sepsis-induced coagulopathy was typically before overt disseminated intravascular coagulation. Interpretation Rapid blood tests, including platelet count, prothrombin time, D-dimer, and neutrophil to lymphocyte ratio can help clinicians to assess severity and prognosis of patients with COVID-19. The sepsis-induced coagulopathy scoring system can be used fo...

Purpose of review The purpose of this article is to describe the function of the vascular cell adhesion and signaling molecule, PECAM-1, in endothelial cells, with special emphasis on its role in maintaining and restoring the vascular permeability barrier following disruption of the endothelial cell junction. Recent findings In addition to its role as an inhibitory receptor in circulating platelets and leukocytes, PECAM-1 is highly expressed at endothelial cell-cell junctions, where it functions as an adhesive stress-response protein to both maintain endothelial cell junctional integrity and speed restoration of the vascular permeability barrier following inflammatory or thrombotic challenge. Summary Due to the unique ability of antibodies that bind the membrane-proximal region of the extracellular domain to trigger conformational changes leading to affinity modulation and homophilic adhesion strengthening, PECAM-1 might be an attractive target for treating vascular permeability disorders.