Home monitoring of blood thinners is as safe as clinic testing, but not superior

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NEW ORLEANS—Home monitoring of clotting speed is as safe as clinic monitoring in patients taking warfarin, but researchers failed to find any superiority for home testing, according to the THINRS trial presented Wednesday at the American Heart Association (AHA) Scientific Sessions.

The study’s co-chair, Alan K. Jacobson, MD, a cardiologist at the Jerry L. Pettis Memorial Veterans Administration (VA) Medical Center in Loma Linda, Calif., presented the results of THINRS (A Prospective Randomized Controlled Trial of the Impact of Home INR testing on Clinical Outcomes: The Home International Normalized Ratio Study).

The researchers randomized 2,922 patients to one of the two testing methods and followed them for an average of three years. During that time, 7.9 percent of the home testing participants had the composite endpoint of stroke, major bleeds or death compared to 8.9 percent of the clinically tested patients, according to Jacobson.

“There was a slight trend toward weekly home monitoring providing a minor improvement over monthly clinic monitoring, but it failed to reach statistical or clinical significance,” Jacobson said. “Once a month at the clinic seems to be just as good as weekly testing at home for most patients.”

Home testing might be the better choice in certain situations, such as for patients whose disabilities or distance from a clinic might keep them from appointments, Jacobson said.

The participants in the randomized study were among 3,745 veterans being treated with the anticoagulant warfarin at 28 VA hospitals across the U.S. The patients had either an irregular heart beat called atrial fibrillation (AF) or had received a mechanical heart valve. They also were trained to use the home monitors, which measure how quickly the blood clots, to reduce any effect the training might have on the study results.

In addition to the unpleasantness of drawing blood and the constant risk that patients may decide to skip appointments—particularly when blood draws are involved, even though it only requires about four drops of blood—many veterans must travel long distances to reach a clinic.

“What we did show was that home testing is every bit as effective as regular clinic monitoring,” said Jacobson, whose clinic has been using at-home testing since 1995 with a special computerized system. “For patients where access is a problem either because of disability or distance, this potentially has a huge impact.”

The bad news is that we didn’t show home monitoring to be superior. The good news is that patients using home monitoring did every bit as well as the patients in the clinic,” he noted.