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Patients who monitor themselves at home for proper dosing of the blood thinner warfarin seem to do just as well as patients who are monitored in a doctor's office, according to a study published in the New England Journal of Medicine.  

“These findings are somewhat surprising because you might expect weekly home monitoring to work better than clinic monitoring, which is typically done each month, providing less opportunity to adjust the medication dose,” said the study’s co-lead author, David Matchar, MD, an internist with the Durham Veterans Affairs Medical Center, Duke University School of Medicine and Duke-NUS Graduate Medical School in Singapore. 

“Home monitoring does appear to be a viable option, especially for patients who find clinic visits present geographic or physical challenges,” he added.

Matchar said when used properly, warfarin can effectively prevent the development of blood clots that can lead to complications, such as strokes. But it requires careful monitoring and is often underused and misused due to difficulties in administering the medication.

“Finding and maintaining a proper dose requires a delicate balancing act -- a low dose won’t prevent potentially deadly blood clots and a high dose can cause serious internal bleeding,” Matchar said.

Several hand-held finger stick devices have been approved by the Food and Drug Administration for home use. Patients are trained to use the devices, which measure international normalized ratio (INR) or how fast the blood clots. The results are phoned in to a physician’s office to discuss altering the medication dose as needed.

Medicare coverage is available for patients with a mechanical heart valve or people taking the pill long-term, such as those with an abnormal heart rhythm, known as atrial fibrillation.

The study included nearly 3,000 veterans at 28 sites who were followed for anywhere from two to nearly five years. Patients with a mechanical heart valve or atrial fibrillation were randomly assigned to conduct weekly home testing or the traditional monthly monitoring in a clinic.

The primary outcome measures were strokes, major bleeding incidents, and death, which were similar between the two groups.

“We found that self-testing was approximately equal, not better, for reducing stroke, major bleeding or death,” said Rowena Dolor, MD, a study co-author and assistant professor of internal medicine at the Durham VA Medical Center and Duke University School of Medicine.

“However, with home monitoring we saw an increase in the amount of time that patients were receiving the proper dose of warfarin. They also reported improved satisfaction and general quality of life.”

The research team concluded that monitoring, regardless of how it is conducted, improves outcomes for patients.

The study co-lead author is Alan Jacobson, MD, at Loma Linda VA Medical Centerand Loma Linda University School of Medicine. Other co-authors include Robert Edson, Lauren Uyeda, Ciaran Phibbs, Julia Vertrees, Mei-Chiung Shih, Mark Holodniy and Philip Lavori. Clinical events were reviewed and verified by faculty at the Duke Clinical Research Institute.

The study was sponsored by VA’s Cooperative Studies Program, part of the VA Office of Research and Development.

Matchar has received consulting fees from Boehringer Ingelheim and honoraria from Roche.