COVID-19-related thrombosis in Japan: Results of a questionnaire-based survey in 2020

Background : COVID-19 became pandemic. Many reportssuggest that thrombosis is intimately involved in clinical deterioration of COVID-19 patients. However, data on COVID-19-related thrombosis in Japan were limited. Aims : A questionnaire-based survey was conducted in order to characterize COVID-19-related thrombosis in Japan by the joint survey team including members of JSTH. Methods : A questionnaire was sent to 399 hospitals throughout Japan. Results : Responses were received from 111 (27.8%) with information on 6,202 COVID-19 patients hospitalized before Aug 31, 2020. Of these, 333 and 56 required ventilation or extracorporeal membrane oxygenation (ECMO), respectively, and 212 died (3.4%). D-dimer levels were measured in 75.0% of the patients, revealing that 9.2% and 7.6% exhibited D-dimer increases of 3-8-fold and ≥8-fold the reference value, respectively. Thrombotic events occurred in 108 patients (1.86% of the 5,807 patients with available data) including symptomatic cerebral infarction in 24, myocardial infarction in 7, deep vein thrombosis in 41, pulmonary thromboembolism in 30, and other thrombotic events in 22. Some patients developed multiple thrombotic events. Thrombosis occurred in 32 patients with mild or moderate COVID-19 severity (0.59% of those with data available) and in 52 patients on ventilation or ECMO (13.5% of severe patients for whom data were available). Thrombosis occurred in 67 patients during worsening clinical condition and in 26 during recovery. Anticoagulant therapy was provided to 893 patients (14.6% of the 6,119 patients with available data), the main reasons being provided as elevated D-dimer levels and worsening clinical condition. Conclusions : Thus, the incidence of thrombotic events in mild/moderate COVID-19 patients in Japan might be much lower than that in the Western countries, while that in severe COVID-19 patients seems comparable/or slightly lower. Of the thromboses, although deep vein thrombosis and pulmonary thromboembolism were most frequent, symptomatic cerebral infarction was also frequent, occurring as 22% of thromboses, which might be a feature specific to Japanese.