Thirteen-year trend in the persistence with vitamin K antagonists for venous thromboembolism in the UK: a cohort study.

BACKGROUND: Venous thromboembolism (VTE) comprises deep vein thrombosis (DVT) and pulmonary embolism (PE) and is associated with significant recurrence and mortality risk. Standard VTE treatment includes at least 3 months anticoagulation. The objective was to describe time trends in the duration of oral anticoagulation in patients initially treated with vitamin K antagonists (VKAs). METHODS: A retrospective cohort study was conducted on patients with first VTE and VKA treatment initiation within 30 days, identified from the UK Clinical Practice Research Datalink from 2001 to 2014. VKA users were followed for the duration of oral anticoagulation which included switching to non-VKA oral anticoagulants. The probability of remaining on anticoagulation treatment (persistence) was estimated using Kaplan-Meier survival functions. RESULTS: A total of 16,018 patients with VTE initiated VKA; 48.2% males, mean age 62.1 years, median VKA treatment duration 6.5 months. The 90-day persistence increased from 75.6% in 2001 to 91.2% in 2013 (p < .0001) and the 180-day persistence from 39.3% in 2001 to 61.1% in 2013 (p < .0001). This time trend was also shown for patients with DVT, PE, provoked VTE, unprovoked VTE, provoked DVT, unprovoked DVT, provoked PE and unprovoked PE. There were no major differences in persistence between patients with provoked and unprovoked VTE, but persistence was lower following DVT than PE (p < .0001). CONCLUSIONS: The increase in persistence was independent of the presentation of the first VTE (provoked or unprovoked), but higher for first PE. Whether the increasing persistence resulted in decreasing risk of recurrent VTE needs to be confirmed.