Clot Risk Low for Outpatients with COVID-19 - European Medical Journal

Clot Risk Low for Outpatients with COVID-19

A STUDY has found that overall venous thromboembolism (VTE) risk for outpatients with COVID-19 is generally low. However, higher risk rates were identified for those who have experienced VTE in the past, for those of older age, and for patients with thrombophilia. 

The study, carried out by the University of California, San Francisco, USA, included 398,530 outpatients who had tested positive case of COVID-19 at either Kaiser Permanente Northern California or Kaiser Permanente Southern California between January 2020–March 2021. Mean patient age was 44 years, and 54% of participants were female.  

The number of VTE events reported by study participants was 292 in 0.1% of this cohort (0.26 per 100 person/years; 95% confidence interval: 0.24–0.30). This rate is similar to that in the general population (0.1–0.2 per 100 person/years). The heightened risk period was in the first 30 days following diagnosis with COVID-19 (0.58 per 100 person/years; 95% confidence interval: 0.51–0.67). 

Lead study author, Margaret C. Fang, University of California, San Francisco, stated: “We identified several subgroups of patients with VTE rates that reached or exceeded the threshold of 4 per 100 person/years, which is when more intensive VTE prevention should be considered.” These subgroups included patients with a prior VTE (12.44 per 100 person/years in the first 30 days), patients with primary or secondary thrombophilia (4.16 per 100 person/years), and patients aged between 75–84 (3.96 per 100 person/years). 

Routine use of anticoagulants in outpatients with COVID-19, or patients who have been recently hospitalised, is not recommended by the current American Society of Hematology (ASH) guidelines. Despite prior trials of anticoagulants demonstrating benefits in certain patients hospitalised with COVID-19, recent studies in outpatients have shown no benefit in their use. Fang commented: “Although the low rates of VTE reported in our study do not support the universal use of antithrombotic agents in non-hospitalised patients with COVID-19, our results support the importance of clinical trials that are evaluating whether some higher-risk subgroups may benefit.” 

The authors suggest that their study provides an opportunity for practitioners to offer targeted interventions for patients, and to increase monitoring in the short-term. A limitation of the study is that it was carried out before the widespread availability of vaccinations for COVID-19. 

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