Assessment of the Risk of Venous Thromboembolism in Nonhospitalized Patients With COVID-19, 2023, Margaret C. Fang et al

Question
What is the risk of venous thromboembolism (VTE) among outpatients with COVID-19?

Findings
In this cohort study of 398 530 adult outpatients with COVID-19, the rate of VTE was low in the first 30 days after COVID-19 diagnosis and even lower after 30 days of follow-up. Factors associated with a higher risk of VTE in COVID-19 included age 55 years or older, being male, a history of VTE or thrombophilia, and body mass index greater than or equal to 30.0.

Meaning
The findings of this study suggest that the overall risk of VTE among outpatients with COVID-19 is low, but higher in the first 30 days after diagnosis.

Abstract
Importance
Patients hospitalized with COVID-19 have higher rates of venous thromboembolism (VTE), but the risk and predictors of VTE among individuals with less severe COVID-19 managed in outpatient settings are less well understood.

Objectives
To assess the risk of VTE among outpatients with COVID-19 and identify independent predictors of VTE.

Design, Setting, and Participants
A retrospective cohort study was conducted at 2 integrated health care delivery systems in Northern and Southern California. Data for this study were obtained from the Kaiser Permanente Virtual Data Warehouse and electronic health records. Participants included nonhospitalized adults aged 18 years or older with COVID-19 diagnosed between January 1, 2020, and January 31, 2021, with follow-up through February 28, 2021.

Exposures
Patient demographic and clinical characteristics identified from integrated electronic health records.

Main Outcomes and Measures
The primary outcome was the rate per 100 person-years of diagnosed VTE, which was identified using an algorithm based on encounter diagnosis codes and natural language processing. Multivariable regression using a Fine-Gray subdistribution hazard model was used to identify variables independently associated with VTE risk. Multiple imputation was used to address missing data.

Results
A total of 398 530 outpatients with COVID-19 were identified. The mean (SD) age was 43.8 (15.8) years, 53.7% were women, and 54.3% were of self-reported Hispanic ethnicity. There were 292 (0.1%) VTE events identified over the follow-up period, for an overall rate of 0.26 (95% CI, 0.24-0.30) per 100 person-years. The sharpest increase in VTE risk was observed during the first 30 days after COVID-19 diagnosis (unadjusted rate, 0.58; 95% CI, 0.51-0.67 per 100 person-years vs 0.09; 95% CI, 0.08-0.11 per 100 person-years after 30 days). In multivariable models, the following variables were associated with a higher risk for VTE in the setting of nonhospitalized COVID-19: age 55 to 64 years (HR 1.85 [95% CI, 1.26-2.72]), 65 to 74 years (3.43 [95% CI, 2.18-5.39]), 75 to 84 years (5.46 [95% CI, 3.20-9.34]), greater than or equal to 85 years (6.51 [95% CI, 3.05-13.86]), male gender (1.49 [95% CI, 1.15-1.96]), prior VTE (7.49 [95% CI, 4.29-13.07]), thrombophilia (2.52 [95% CI, 1.04-6.14]), inflammatory bowel disease (2.43 [95% CI, 1.02-5.80]), body mass index 30.0-39.9 (1.57 [95% CI, 1.06-2.34]), and body mass index greater than or equal to 40.0 (3.07 [1.95-4.83]).

Conclusions and Relevance
In this cohort study of outpatients with COVID-19, the absolute risk of VTE was low. Several patient-level factors were associated with higher VTE risk; these findings may help identify subsets of patients with COVID-19 who may benefit from more intensive surveillance or VTE preventive strategies.

https://jamanetwork.com/journals/jamanetworkopen/fullarticle/2802356