Anticoagulation Length of ThErapy and Risk of New Adverse evenTs In Venous thromboEmbolism Study

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 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 of this study are 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:

- Any oral anticoagulant prescription within 12 months before the index VTE date.