Abstract: Thrombosis Research 198 (2021) 19–22 Contents lists available at ScienceDirect Thrombosis Research journal homepage: www.elsevier.com/locate/thromres Letter to the Editors-in-Chief Low molecular weight heparin and 28-day mortality among patients with coronavirus disease 2019: A cohort study in the early epidemic era Patients with COVID-19 and preexisting diseases are likely to have poor outcomes. Coagulopathy is a prominent clinical manifestation and coagulation markers are recognized as haematological risk factors for mortality. Anticoagulant use is an important supportive treatment that may benefit patient survival. Preliminary data showed that anticoagu­ lant therapy was associated with lower mortality in severe patients with markedly elevated D-dimer [1]. However, data on anticoagulation use in Chinese patients during the early pandemic era are limited. The asso­ ciations of Low Molecular Weight Heparin (LMWH) and other available treatments with patients’ prognoses are not well established. Therefore, we report our initial experience in treatments for COVID-19 hospitalized patients, particularly the use of LMWH. A pragmatic cohort study was performed, involving adult patients with PCR-confirmed COVID-19 consecutively admitted to the affiliated hospital of Jianghan University between January 10th, 2020 and February 28th, 2020. Patients were followed for 28 days after admis­ sion. COVID-19 infection was diagnosed according to the Chinese management guideline (Trial Version 5 Revised, http://www.nhc.gov. cn/yzygj/s7653p/202002/d4b895337e19445f8d728fcaf1e3e13a.sh tml). We obtained ethical approval from the Medical Ethics Committee of Affiliated Hospital of Jianghan University and China-Japan Friend­ ship Hospital (WHSHIRB-K-2020015) on April 21, 2020. Subcutaneous LMWH (Low Molecular Weight Heparin Sodium for Injection, Jiangsu Wanbang Biochemical Pharmaceutical Co. LTD, China) use was recor­ ded, administered as prophylactic dosage 3000–5000 U/day or the therapeutic dose was based on actual body weight (100 U/kg, q12h). All patients were given intravenous methylprednisolone according to our guideline, 40 or 80 mg/day. The primary outcome was mortality within 28 days after hospital admission. Patients discharged earlier were fol­ lowed to day 28 to ascertain survival. Data were summarized as number (percentage) for categorical var­ iables and mean (SD) or median (interquartile ranges [IQR]) for continuous variables as appropriate. t-test, Mann Whitney U test, Chisquare test or Fisher exact test were used to compare differences in baseline characteristics, treatment and complications. To explore an association of LMWH treatment with 28-day mortality, we fitted multivariable Cox regression model with covariates adjusted. The pro­ portional hazard assumption was tested and if the assumption was violated, an extended Cox analysis with time-varying covariates was performed. The violating covariates were handled by their interactions with followed-up time. Patients alive at day 28 were regarded as rightcensored. Based on the up-to-date knowledge on COVID-19 and prior research, we constructed a causal diagram to visually illustrate the po­ tential effect of exposures on fatal outcomes (Fig.A.1). Five blocks of factors were analyzed: typical demographic information, comorbidities, COVID-19 severity, coagulopathy on admission, and treatments provided in hospital. In our prior research, normal D-dimer on admis­ sion and day 3 were highly..