To the Editor: Patients with coronavirus disease 2019 have a profound hypercoagulable state, and complicating venous thrombotic events are common. [1][2][3] Abnormalities in coagulation screening measures, including a prolonged activated partial-thromboplastin time (aPTT), have been reported in patients with This finding could be seen as a reason to avoid the use of anticoagulation at both therapeutic and prophylactic doses.A prolonged aPTT may indicate a clottingfactor deficiency or the presence of an inhibitor of coagulation that is either specific (e.g., antibody to factor VIII) or nonspecific (e.g., lupus anticoagulant). Lupus anticoagulant can affect in vitro tests of blood coagulation but typically is not associated with bleeding. As part of the antiphospholipid syndrome, lupus anticoagulant is associated with a thrombotic risk. We investigated the cause of prolonged aPTT in patients with Covid-19.Blood specimens obtained from 216 patients who were positive for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) were received for coagulation screening, and 44 (20%) were found to have a prolonged aPTT. The specimens from 9 patients were excluded, and those from 35 patients were investigated further. (Details of the methods are provided in the Supplementary Appendix, available with the full text of this letter at NEJM.org.)A summary of the results is provided in Table 1. The median age was 57 years, and 24 patients were male. Pulmonary embolism was confirmed in 1 patient, and clinically suspected thrombosis was present in 1 patient. No clinically significant bleeding or arterial thromboses were reported.No patients were found to have deficiencies in factor VIII or factor IX. In 5 patients, marginal reductions in factor XI were found that were un-

Objective-To identify an appropriate diagnostic tool for the early diagnosis of Acute Traumatic Coagulopathy (ATC) and validate this modality through prediction of transfusion requirements in trauma hemorrhage. This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final citable form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. Design-Prospective observational cohort study Setting-Level 1 trauma centre Europe PMC Funders Group Europe PMC Funders Author Manuscripts Europe PMC Funders Author ManuscriptsPatients-Adult trauma patients who met the local criteria for full trauma team activation. Exclusion criteria included emergency department (ED) arrival >2 hours after injury, >2000ml of intravenous fluid before ED arrival or transfer from another hospital. Interventions-NoneMeasurements-Blood was collected on arrival in ED and analysed with laboratory prothrombin time (PT), point of care (PoC) PT and rotational thromboelastometry (ROTEM). Prothrombin ratio (PTr) was calculated and ATC defined as laboratory PTr>1.2. Transfusion requirements were recorded for the first 12 hours following admission.Main Results-300 patients were included in the study. Laboratory PT results were available at median 78 (62-103) minutes. PoC PTr had reduced agreement with laboratory PTr in patients with ATC, with 29% false negative results. In ATC the ROTEM Clot Amplitude at 5 minutes (CA5) was diminished by 42% and this persisted throughout clot maturation. ROTEM clotting time was not significantly prolonged. A CA5 threshold ≤35mm had a detection rate of 77% for ATC with a false positive rate of 13%. Patients with CA5 ≤35mm were more likely to receive red cell (46% vs 17%, p<0.001) and plasma (37% vs 11%, p<0.001) transfusions. The CA5 could identify patients who would require massive transfusion (detection rate of 71%, vs 43% for PTr >1.2, p<0.001).Conclusions-In trauma hemorrhage PTr is not rapidly available from the laboratory and PoC devices can be inaccurate. ATC is functionally characterised by a reduction in clot strength. With a threshold of CA5 ≤35mm ROTEM can identify ATC at 5 minutes and predict the need for massive transfusion.