Small-area analysis of treatment and clinical outcomes in patients with venous thromboembolism in Denmark: a nationwide cohort study.

Objectives To investigate geographical variation in initiation and long-term treatment with anticoagulants and clinical outcomes among patients hospitalized with first-time venous thromboembolism (VTE) in Denmark between 2007 and 2018. Methods Using nationwide health care registries, we identified all patients with a first-time VTE hospital diagnosis supported by imaging data from 2007 to 2018. Patients were grouped according to residential region (5) and municipality (98) at the time of VTE diagnosis. Cumulative incidence of initiation and long-term (beyond 365 days) treatment with anticoagulants as well as clinical outcomes, including recurrent VTE, major bleeding and all-cause death, were assessed. Sex- and age-adjusted relative risk (RR) of the outcomes were compared across regions and municipalities. Results: We identified 66,846 patients with a first-time VTE hospitalization. A difference in initiation of anticoagulation treatments of more than 20 percentage points between regions was observed. The geographical variation in initiation and persistence was statistically significant both at regional and municipality level (p<0.0001). The cumulative incidence of recurrent VTE ranged from 3.6-5.3% at 1 year. The difference remained after 5 years and variation was also observed for major bleeding and all-cause mortality (p<0.0001). Conclusions Substantial geographical variation in anticoagulant use and clinical outcomes occurs in Denmark, thus demonstrating unwarranted variation in VTE care and clinical outcomes. These findings indicate a need for systematic quality of care improvement initiatives ensuring uniform high-quality care for all VTE patients.