Knut Stavem

Introduction COVID‐19 is associated with an increased risk of venous thromboembolism (VTE), but there is great variation among reported incidence rates. Most previous studies have focused on hospitalized patients with COVID‐19, and only a few reports are from population‐based registries. Methods We studied the 90‐day incidence of VTE, associated risk factors and all‐cause mortality in hospitalized and nonhospitalized patients with COVID‐19 in a nationwide cohort. Data on hospitalizations and outpatient visits were extracted from two national registries with mandatory reporting linked by a unique national identification number carried by all Norwegian residents. We performed Cox proportional hazards regression to determine risk factors for VTE after infection with SARS‐CoV‐2. Results Our study included 30,495 patients with positive SARS‐CoV‐2 polymerase chain reaction with a mean (SD) age of 41.9 (17.3) years, and 53% were males. Only 2081 (6.8%) were hospitalized. The 90‐day incidence of VTE was 0.3% (95% CI: 0.21–0.33) overall and 2.9% (95% CI: 2.3–3.7) in hospitalized patients. Age (hazard ratio [HR] 1.28 per decade, 95% CI: 1.11–1.48, p < 0.05), history of previous VTE (HR 4.69, 95% CI: 2.34–9.40, p < 0.05), and hospitalization for COVID‐19 (HR 23.83, 95% CI: 13.48–42.13, p < 0.05) were associated with risk of VTE. Conclusions The 90‐day incidence of VTE in hospitalized and nonhospitalized patients with COVID‐19 was in the lower end compared with previous reports, with considerably higher rates in hospitalized than nonhospitalized patients. Risk factors for VTE were consistent with previously reported studies.