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Warfarin Self-Monitoring Offers Benefits

February 13, 2006 -- People who take anti-clotting drug warfarin and self-monitor their blood levels, rather than having a laboratory monitor them, may be much better off, according to a study published in The Lancet and reported by on February 3, 2006.

Warfarin is marketed in the US under brand-name Coumadin.

Researchers Dr Carl Heneghan, a clinical research fellow at Oxford, and colleagues found that people who monitor their own blood warfarin levels have a significantly lower risk of major adverse events and mortality.

The purpose of the study was to "fill a knowledge gap", according to HealthDay, and the researchers wrote about the self-monitoring technique, "Published guidelines state that there are no reliable clinical-outcome data in any of the published studies to lend support to its use."

In contrast, Dr Heneghan and colleagues analysis showed that, in fact, "Self-management improves the quality of oral anticoagulation."

Clinical Trial

The study involved a review of 14 randomized, controlled clinical trials and measured endpoints of major hemorrhage, thromboembolic events, death, tests in range, minor hemorrhage, test frequency and feasibility of self-monitoring.

The results showed that self-monitoring was associated with a 55% lower rate of harmful clotting events, a 39% lower death rate (from all causes) and a 35% lower rate of major bleeding crises, compared with laboratory monitoring.

Lead author Dr Heneghan said that the study was initially intended only to demonstrate the safety of self-monitoring, according to The additional findings that self-monitoring is associated with substantial health benefits was surprising.

"Each of the trials alone was not statistically significant, but combining them showed that you get a benefit in terms of mortality," he said, according to He added that warfarin self-monitoring may be compared to people with diabetes' self-monitoring their blood sugar levels.

"It offers a sense of freedom, of not being tied to a clinic," he reportedly said.

Warfarin reduces the clotting ability of blood, but is difficult to manage and required constant monitoring with blood tests to ensure that the person's blood can still clot within the normal range. People who take Coumadin must often test themselves weekly or every few weeks, for years.

A Low Rate of Self-Monitoring

The US Food and Drug Administration (FDA) has approved warfarin self-monitoring equipment, but less than 1% of doctors permit their patients to self-monitor, according to Gary Liska, director of the disease management group of the company Quality Assured Services, which markets three types of monitor.

One reason for the low rate of self-monitoring is that Medicare will cover the cost of the equipment only for people who have artificial heart valves, Liska reportedly said. However, warfarin may be prescribed for several other reasons, such as atrial fibrillation.

Liska also noted that perhaps medical professionals "fear of loss of control of patients. We feel that in reality the opposite is true, that patients have better control than ever before."

Fear of malpractice suits is another concern, in cases where self-monitoring goes awry. For example, warfarin interacts with several other drugs, and the risk of harmful drug-drug interactions is increased in the elderly population, who often take several medications at once. (To find out about the interactions between warfarin and other drugs, please visit the Drug Interactions Checker.)

Intensive patient training and the high cost of test-strips may also contribute to the low rate of self-monitoring. However, once people learn the technique, the test requires only a fingerstick, similar to the test that people with diabetes perform to measure blood glucose.

If a warfarin-level reading is outside the range set by their physician, the person can call the doctor to find out about changing their dosage.

However, with regard to patients being able to self-monitor their own warfarin levels, "many doctors seem to have a roadblock in their minds," Liska reportedly said.

Self-Monitoring of Blood Drug Helps Patients,, February 3, 2006.
Self-monitoring of oral anticoagulation: a systematic review and meta-analysis. C Heneghan et al, The Lancet, volume 367, pages 404-411, February 2006.

Posted: February 2006