Risk factors for VTE among COVID-19 patients included age greater than 55 years, male gender, a history of thrombophilia, and obesity.
The risk for venous thromboembolism (VTE) among patients with COVID-19 is low, but certain patient characteristics were associated with higher rates of VTE especially in the first 30 days post-diagnosis, according to an original investigation published in JAMA Network Open.
Investigators from California conducted a retrospective cohort study of nearly 400000 adult outpatients with COVID-19 at 2 integrated health care systems in order to determine the risk of VTE among these outpatients. The study authors also aimed to identify independent predictors of VTE among this cohort.
VTE has been noted as an important complication of COVID-19, especially among hospitalized or critically ill patients; these patients have a substantially increased risk compared to hospitalized patients without COVID-19.
Illustrating the importance of measuring this occurrence, the study authors said, was the fact that a recent clinical trial that investigated prehospitalization prophylaxis against VTE in COVID-19 was discontinued due to a lower-than-expected event rate.
“Accurate assessments of the true risk of VTE are necessary to guide recommendations on prevention and surveillance strategies,” the study authors wrote.
Patients in this study were diagnosed with lab-confirmed COVID-19 tests between January 1, 2020, and January 31, 2021. The patients were followed up with through February 28, 2021, with data including death, health plan disenrollment, or hospitalization due to COVID-19.
The investigators identified 398530 adults with COVID-19, a group that averaged 43.8 years and 53% female. The study authors also reported that 10% of the patients were Asian or Pacific Islander, 6% were Black, 75% were White, and 54% self-reported Hispanic ethnicity. Almost none of the nonhospitalized patients in the study had a documented prior VTE (0.3%) or baseline oral anticoagulant use (1.1%).
Total VTE events numbered 292, for an overall rate of 0.26 per 100 person-years. From that group, the study authors further categorized the events:
The median time between COVID-19 diagnosis and the date of VTE events was 19 days, the study authors found. They observed that factors associated with higher rates of VTE included age 55 years or older, male gender, prior VTE, known thrombophilia, and obesity.
“In this cohort study of outpatient adults with COVID-19, we found that although the absolute risk of VTE was low overall, selected patient characteristics were associated with higher rates of VTE, particularly in the first 30 days after COVID-19 diagnosis,” the study authors wrote.
These findings are aligned with other published literature. For example, the investigators cited a Swedish study that showed COVID-19 patients with all levels of severity demonstrated an absolute risk of pulmonary embolism of 0.17% in the first 30 days after COVID-19 diagnosis. They noted there was a higher risk during the initial presentation among older patients.
“These findings may help identify subsets of patients with COVID-19 who could benefit from VTE preventive strategies and more intensive short-term surveillance,” the study authors concluded.