(HealthDay News) — A new small study raises more questions about the accuracy of home blood pressure monitoring devices

The research is scheduled to be presented at the American Society of Nephrology’s Kidney Week 2014, held from Nov. 11 to 16 in Philadelphia.

Swapnil Hiremath, MD, of The Ottawa Hospital and University of Ottawa in Canada, and colleagues looked at data from 210 patients — 60%men, with an average age of 67 years — who brought their blood pressure (BP) monitors to the doctor’s office.

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“Our nurse, an RN, would measure blood pressure in both arms using the office blood pressure machine,” Hiremath told HealthDay. “Once it was confirmed that there was no difference between arms, measurements were taken in both arms simultaneously — one with the home machine, one with the office machine. Since the data we report is from measurements taken by the RN, this is not a case of patient error.” 

The office machine was considered to be accurate.

On average, the systolic and diastolic BP readings were only a few points off in the home devices. Between 30% and 32% of the time, the BP readings were off by 5 mm Hg with the home devices. But the readings were off by more than 10 mm Hg — a difference that could be significant — between 8% and 9% of the time.

How much might the differences matter? It’s hard to say, Hiremath said. 

In some cases, an inaccurate reading might not result in a different treatment compared with an accurate reading. A reading of, say, “155 vs. 166 will still often result in the same decision,” he said. But it’s also possible that a small difference could mislead a physician and result in a different kind of decision, he added.

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