Grant: CIHR-ICRH Travel Awards - General pool

After completing 3 to 6 months of initial treatment for unexplained blood clots either in the leg veins or the lung arteries, collectively knows as venous thromboembolism (VTE), clinical practice guidelines suggest continuing treatment with blood thinners for life over discontinuing treatment. However, whether lifelong treatment provides a survival benefit or is cost-effective, particularly in relevant patient subgroups, has not been formally assessed. We created a mathematical model to simulate costs and quality-adjusted life expectancy for two hypothetical cohorts of patients aged 55 years with an unexplained VTE that had completed 3 to 6 months of initial treatment – one cohort assigned to continue treatment lifelong and another assigned to discontinue treatment for life. The economic analysis adopted a third-party payer perspective relating to the Canadian publicly-funded healthcare system. We examined the following patient subgroups: men, women, patients with an initial blood clot in the leg veins, patients with an initial blood clot in the lung arteries, patients aged 35 years, and patients aged 75 years. We found that in patients with an initial blood clot in the lung arteries, lifelong treatment with blood thinners cost $12,014 more and added 45 days of perfect health per person, with a 80% chance of increasing quality-adjusted life expectancy and a 24% chance of being cost-effective. In all other patient subgroups, lifelong anticoagulation was incurred higher costs and no improvement in life expectancy. We also found that an annual risk of major bleeding associated with blood thinners below 0.67% was required for lifelong treatment to provide a survival benefit. These findings emphasize that lifelong treatment with blood thinners might provide a mortality benefit in certain subgroups including patients with an initial blood clot in the lung arteries or those at a very low risk for bleeding. However, lifelong treatment is unlikely to ever be cost-effective.