At-Home Blood Pressure Monitoring Devices Are Often Inaccurate

Be wary if an at-home system is monitoring your blood pressure or that of a loved one — they’re inaccurate seven out of 10 times, says a new study.

High blood pressure, which is known as the “silent killer,” affects about one-third of the U.S. adult population, or about 75 million people. A person has normal blood pressure when their upper number is less than 120 mmHg and the lower figure is under 80 mmHg.

Yet the study found that home-monitoring systems often failed to record an accurate measurement, which could lead physicians to mistakenly believe a patient’s numbers are better than they appear. About 70 percent of the time, the monitoring systems failed to get within 5 mmHg of a person’s actual blood pressure reading.

“Guidelines are recommending that clinicians rely more on automatic and home blood pressure readings to diagnose and monitor high blood pressure,” lead author Jennifer Ringrose told Reuters Health. “We need to make sure these home blood pressure readings are accurate.”

Check the Device, Ask Doctor About It

Nearly one-third of the time, the at-home systems were off by 10 mmHg or more, according to the study. The researchers assessed 85 patients and compared the results from the remote electronic systems with those gained using a traditional blood pressure cuff in the doctor’s office.

“There can be substantial error, even in devices that have been tested in a validation study,” senior study author Raj Padwal, who is affiliated with the Mazankowski Heart Institute in Alberta, told Reuters.

The fact that private companies keep their technology close to the vest makes discerning the numbers a difficult task.

Related: The Key to Lower Blood Pressure Might Be in Your Inbox

“A major issue is that it is hard to study why inaccuracies occur because the algorithm that these devices use to determine blood pressure is proprietary and kept secret by each company,” Padwal said, according to Reuters.

Yet the researchers believe the current study can help fine tune a remote-technology market that’s growing by leaps and bounds as the country ages and rates of hypertension increase.

“The market for this equipment is rising dramatically into the billions in the next couple of years as patients age, and more doctors are using them to diagnose and manage hypertension,” Marcel Ruzicka of the University of Ottawa told Reuters.

To ensure your readings are as accurate as possible, “patients should purchase a validated monitor and use the proper sized cuff,” Padwal said.

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The new study also gives patients another question to add to their list when they visit the doctor for an appointment — namely, how close your at-home readings are to what the doctor is seeing in the office and how often your device should be looked over to ensure accuracy.

“As health care providers, we’re becoming more dependent on the numbers that patients are bringing to us, and in a busy office where you can’t get a true resting blood pressure, those may be the only numbers you have,” Ruzicka told Reuters.

“It’s important to be aware that this inaccuracy is out there,” Ruzicka said. “Next, we should ensure that accuracy checks are widely available and not cost prohibitive for device owners.”