Despite the advent of newer anticoagulants that don’t require monitoring, millions of people will continue to take warfarin for many years to come. Now a new meta-analysis published in the Lancet suggests that some of these patients may benefit from self-monitoring.
Carl Heneghan and colleagues analyzed data from 11 trials with 6,417 participants and 12,800 person-years of followup. They found a significant reduction in thromboembolic events for self-monitoring patients but not for major hemorrhagic events or for death. Patients who were 55 years old or younger and patients with mechanical heart valves had large reductions in thrombotic events.
Hazard ratios and 95% confidence intervals for the self-monitoring group and subsets:
- Thromboembolic events: HR 0·51, 0·31–0·85
- Major hemorrhagic events HR 0·88, 0·74–1·06
- Death: HR 0·82, 0·62–1·09
- Thrombotic events in patients <55 years: HR 0·33, 0·17–0·66
- Thrombotic events in patients with mechanical heart valve: HR 0·52, 0·35–0·77).
The authors calculated that 21 patients under the age of 55 would need to self-monitor for one year to prevent one thromboembolic event. For mechanical valve patients the NNT was 55.
In an accompanying comment, Paul Alexander Kyrle and Sabine Eichinger write that self-monitoring should “be offered to patients with mechanical heart valves, especially those younger than 55 years. However, we do not see a place for self-monitoring in other areas of this treatment except for individual patients for whom access to routine usual anticoagulation care is restricted.”
Here is the Lancet press release:
Self-monitoring of blood-thinning treatment almost halves risk of developing blood clots compared with conventional care (The Lancet)
Patients who self-monitor their oral anticoagulation (blood-thinning) therapy with vitamin K antagonists (VKA) such as warfarin nearly halve their risk of developing thromboembolic events such as deep vein thrombosis, stroke, and heart attack compared with those receiving conventional care, according to a meta-analysis published Online First in The Lancet.
In the UK, approximately a million people are eligible for oral anticoagulation therapy and more than 4 million patients in Europe are living with long-term oral anticoagulation because of conditions including cardiac arrhythmias, artificial heart valves, or a previous history of blood clots. Because of an ageing population the demand for oral anticoagulants is set to rise dramatically.
Individual patients respond differently to the same VKA dose and the therapeutic range for VKA is narrow. Therefore, regular blood monitoring and dose adjustment is necessary to prevent excessive anticoagulation that can result in major bleeding, or inadequate anticoagulation that can expose patients to the potentially fatal blood clots they are used to prevent.
Self-monitoring can improve the quality of anticoagulation and be more convenient for patients. Yet, the use of self-testing (patients test, but dosage is done by physicians) and self-management (patients test and adjust their own doses) has remained inconsistent both in and between countries, ranging from 20% of patients on anticoagulant therapy in Germany to just 1% of patients in the USA.
To provide more evidence of the benefit of self-monitoring, a team led by Carl Heneghan from the University of Oxford, Oxford, UK, pooled individual patient data from 11 randomised trials comparing self-monitoring of oral anticoagulation with conventional care.
They estimated the effect of self-monitoring on time to death, first major bleeding event, first thromboembolic event, and in important subgroups of patients such as the elderly and those with atrial fibrillation (a common and strong risk factor for stroke) and those with a mechanical heart valve.
Overall, self-monitoring reduced the risk of thromboembolic events by 49% compared with usual care. However, the rate of bleeding complications was similar in both groups and self-monitoring did not have a major effect on mortality.
The benefits of self-monitoring were particularly striking in individuals younger than 55 years in whom the likelihood of developing thromboembolic events was reduced by two-thirds and patients with a mechanical heart valve whose risk was halved.
Interestingly, self-monitoring lowered mortality and did not increase complications in very elderly patients who are at high risk of major bleeding, suggesting that age should not be a factor in determining eligibility for self-management.
The authors conclude: “Self-monitoring and self-management of oral coagulation is a safe option for suitable patients of all ages. Patients should also be offered the option to self-manage their disease with suitable health-care support as back-up.”
In a Comment, Paul Alexander Kyrle and Sabine Eichinger from the Medical University of Vienna, Vienna, Austria, say: “Self-management (rather than self-testing) of treatment with vitamin K antagonists should be offered to patients with mechanical heart valves, especially to those younger than 55 years. However, we do not see a place for self-monitoring in other areas of this treatment except for individual patients for whom access to routine usual anticoagulation care is restricted.”