The proposed research seeks to provide insights on the contemporary epidemiology, treatment, and outcomes of VTE, including examining the uptake of new treatment strategies, the efficacy and safety of different anticoagulant options, and the impact of venous thromboembolism on patient-defined outcomes, such as quality-of-life, symptom burden, and treatment satisfaction. This information is crucial to helping clinicians and patients choose between various treatment options for venous thromboembolism in order to achieve the best possible balance between the risks, benefits, and impact on health.

Venous thromboembolism (VTE) is a leading cause of cardiovascular death and continues to be a major public health issue in the United States. The cornerstone of current VTE treatment is anticoagulation, typically given for ≥ 3 months during the acute phase of thrombosis. Afterwards, extended-duration anticoagulation can be considered for selected higher-risk patients. Treatment options for VTE have expanded substantially in recent years, most notably through the availability of direct oral anticoagulants (DOACs). Yet there are many remaining gaps in the understanding of how to manage VTE to maximize net clinical benefit.

The long-range objective of this project is to reduce the morbidity and mortality associated with VTE in adults and evaluate contemporary treatment patterns and long-term outcomes after VTE. This initial phase of the study will assemble an observational cohort of adults with VTE diagnosed between 2010-2018. Study subjects will be identified from two integrated healthcare delivery systems (Kaiser Permanente Northern California and Kaiser Permanente Southern California) and followed until December, 2019. Data will be obtained from administrative and electronic health records, supplemented with a cross-sectional patient survey.

The first two aims will be to compare the rates of recurrent VTE and hemorrhage between (1) extended anticoagulation vs. no extended anticoagulation after VTE; and (2) DOAC vs. warfarin treatment of VTE. The third specific aim is to describe patient-defined outcomes in adults with VTE in the current treatment era. This will be accomplished by surveying subjects with VTE to collect data on generic and disease-specific quality-of-life as well as on anticoagulant treatment satisfaction. Combining clinical, outcome, and survey data with administrative data will create a contemporary cohort of VTE patients that can serve as a rich source of information for use in facilitating comparative effectiveness research addressing optimal VTE management within real-world practice settings.

Inclusion Criteria:

• Adults (age ≥ 18 years) enrolled in Kaiser Permanente Northern California or Kaiser Permanente Southern California
• Index VTE event, defined as an incident clinical encounter (inpatient, emergency department, or outpatient) with a primary or secondary diagnosis of VTE during the time period January 1, 2010 to December 31, 2018
• Anticoagulant prescription (oral or parenteral) filled after index VTE discharge/encounter date
• Continuous outpatient anticoagulant therapy for ≥ 3 months from fill date of prescription
• Continuous pharmacy benefits and health plan membership for at least 12 months before the index VTE event date

Exclusion Criteria:

- Incomplete information on age and sex

The source populations for the study will be adults diagnosed with acute venous thromboembolism who were enrolled in Kaiser Permanente Northern California or Kaiser Permanente Southern California, two large, integrated healthcare delivery systems in California.