Background Venous thromboembolism (VTE) is a frequent complication of COVID-19, so that the importance of adequate in-hospital thromboprophylaxis in patients hospitalized with COVID-19 is well established. However, the incidence of VTE after discharge and whether postdischarge thromboprophylaxis is beneficial and safe are unclear. In this prospective observational single-center study, we report the incidence of VTE 6 weeks after hospitalization and the use of postdischarge thromboprophylaxis.

Methods Patients hospitalized with confirmed COVID-19 were invited to a multidisciplinary follow-up clinic 6 weeks after discharge. D-dimer and C-reactive protein were measured, and all patients were screened for deep vein thrombosis with venous duplex-ultrasound. Additionally, selected high-risk patients received computed tomography pulmonary angiogram or ventilation–perfusion (V/Q) scan to screen for incidental pulmonary embolism.

Results Of 485 consecutive patients hospitalized from March through June 2020, 146 patients were analyzed, of which 39% had been admitted to the intensive care unit (ICU). Postdischarge thromboprophylaxis was prescribed in 28% of patients, but was used more frequently after ICU stay (61%) and in patients with higher maximal D-dimer and C-reactive protein levels during hospitalization. Six weeks after discharge, elevated D-dimer values were present in 32% of ward and 42% of ICU patients. Only one asymptomatic deep vein thrombosis (0.7%) and one symptomatic pulmonary embolism (0.7%) were diagnosed with systematic screening. No bleedings were reported.

Conclusion In patients who had been hospitalized with COVID-19, systematic screening for VTE 6 weeks after discharge revealed a low incidence of VTE. A strategy of selectively providing postdischarge thromboprophylaxis in high-risk patients seems safe and potentially effective.

背景技术 静脉血栓栓塞症（VTE）是COVID-19的常见并发症，因此，对于COVID-19住院的患者，充分进行院内血栓预防非常重要。然而，尚不清楚出院后VTE的发生率以及出院后血栓预防是否有益和安全。在这项前瞻性观察性单中心研究中，我们报告了住院6周后VTE的发生率以及出院后血栓预防的使用。

方法将 出院确诊为COVID-19的住院患者在出院后6周邀请到多学科随访诊所。测量D-二聚体和C-反应蛋白，并通过静脉双重超声对所有患者进行深静脉血栓形成的筛查。此外，部分高危患者接受了计算机断层扫描肺血管造影或通气-灌注（V / Q）扫描，以筛查偶发的肺栓塞。

结果 从2020年3月至2020年6月，我们对485例住院患者进行了分析，分析了146例患者，其中39％的患者被送往重症监护病房（ICU）。在28％的患者中规定了出院后血栓预防措施，但在住院ICU后（61％）以及住院期间最大D-二聚体和C反应蛋白水平较高的患者中使用血栓的频率更高。出院六周后，在32％的病房和42％的ICU患者中D-二聚体值升高。通过系统筛查仅诊断出1例无症状深静脉血栓形成（0.7％）和1例有症状肺栓塞（0.7％）。没有出血的报道。

结论 在住院COVID-19的患者中，出院后6周进行VTE的系统筛查发现VTE的发生率较低。在高危患者中选择性提供放电后血栓预防的策略似乎是安全且潜在有效的。