There were some differences between groups of patients. People who adjusted their own Coumadin levels after taking blood tests had lower levels of blood clots and death by any cause; those who relied on contacting clinics for instructions on adjusting their doses had lower levels of major bleeding incidents.

It is unclear why the difference exists, although it is possible that people who monitor their own Coumadin levels might think uncontrolled bleeding is less of a big deal than a blood clot and adjust their drug levels accordingly, said review co-author Carl Heneghan, deputy director of Oxford's Centre for Evidence-Based Medicine. As a result, they would keep their Coumadin levels a bit higher than the ideal range.

The review authors also found that about half of patients would not be eligible to monitor their Coumadin levels because they refused to take part in the studies, their physicians deemed them ineligible or they could not get through training.

Cost could be another factor. The monitoring devices cost up to $2,500, although insurance often covers them, said Dr. Henry Bussey, a professor at the University of Texas at Austin's College of Pharmacy who consults for a company that makes software to monitor Coumadin levels.

He said Coumadin self-monitoring does have plenty of benefits. Among other things, it frees patients from feeling as if they must be available to take blood tests at local laboratories. Patients, he said, will not need to avoid travel due to fear of being far from laboratories where they can get blood tests.

However, he said, it is important to make sure doctors are in the loop and adjust Coumadin levels for patients after reviewing blood test results.

SOURCE The Cochrane Library