Are outpatients with COVID-19 at higher risk of venous thromboembolism?

Patients hospitalized with COVID-19 are known to have a higher rate of venous thromboembolism (VTE) compared to hospitalized patients without COVID-19. However, the risk and predictors of VTE among individuals with less severe COVID-19 managed in outpatient settings are less well understood. A greater understanding of VTE risk in outpatients with COVID-19 is needed to help guide thromboprophylaxis strategies. A new U.S. study has assessed the risk of VTE among outpatients with COVID-19. It also identified independent predictors of VTE. The retrospective cohort study was conducted at two integrated healthcare delivery systems in California. The study included a total of 398,530 outpatients with COVID-19 (mean age 43.8 years, 53.7% women). The primary outcome was the rate per 100 person-years of diagnosed VTE. Results showed the following: A total of 292 (0.1%) VTE events were identified over the follow-up period, for an overall VTE rate of 0.26 (95% CI, 0.24–0.30) per 100 person-years. Among the 292 VTE events, 57.5% were pulmonary emboli, 34.9% were lower extremity deep vein thromboses, 5.1% were upper extremity deep vein thromboses, and 2.5% were other VTEs at unusual sites. The sharpest increase in VTE risk was seen during the first 30 days after lab-confirmed COVID-19 diagnosis (unadjusted rate, 0.58; 95% CI, 0.51–0.67 per 100 person-years in the first 30 days vs. 0.09; 95% CI, 0.08–0.11 per 100 person-years after 30 days). The median time between index COVID-19 diagnosis and date of VTE event was 19 days. The following variables were associated with a higher risk for VTE in the setting of nonhospitalized individuals with COVID-19: age 55 to 64 years (hazard ratio [HR] 1.85 [95% CI, 1.26–2.72]), 65 to 74 years (HR 3.43 [95% CI, 2.18–5.39]), 75 to 84 years (HR 5.46 [95% CI, 3.20–9.34]), ≥ 85 years (HR 6.51 [95% CI, 3.05–13.86]) male gender (HR 1.49 [95% CI, 1.15–1.96]) prior VTE (HR 7.49 [95% CI, 4.29–13.07]) thrombophilia (HR 2.52 [95% CI, 1.04–6.14]) inflammatory bowel disease (HR 2.43 [95% CI, 1.02–5.80]) body mass index 30.0–39.9 (HR 1.57 [95% CI, 1.06–2.34]), and body mass index ≥ 40.0 (HR 3.07 [1.95–4.83]). In this study of outpatients with COVID-19, the absolute risk of VTE was low (0.26 per 100 person-years). Several patient-level factors were associated with higher VTE risk, including increasing age, male gender, prior VTE, thrombophilia, inflammatory bowel disease and higher body mass index. The authors note that the rate of VTE found in their study is not much higher than the average rate of VTE in the general population (which is about 0.1–0.2 per 100 person-years). This low observed VTE rate does not justify routine administration of anticoagulation to the average nonhospitalized person with COVID-19, given the associated costs, inconvenience and bleeding risks. However, the authors identified several subgroups of patients with VTE rates that reached or exceeded the threshold of four per 100 person-years (when more intensive VTE prevention should be considered). These included people with a history of VTE, those with a history of primary or secondary thrombophilia, and people 75–84 years of age. Clinical trials are required to determine whether these higher-risk nonhospitalized patients with COVID-19 may benefit from more intensive surveillance or VTE preventive strategies. Reference 1. Fang MC, Reynolds K, Tabada GTH, et al. Assessment of the risk of venous thromboembolism in nonhospitalized patients with COVID-19. JAMA Network Open. 2023;6(3):e232338. (accessed March 16, 2023).

Are outpatients with COVID-19 at higher risk of venous thromboembolism?

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