Popular Blood Pressure App 'Highly Inaccurate,' Study Says
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A popular health app that claims to let people estimate their blood pressure using just their smartphone is "highly inaccurate," according to a new study.

In the study, about 77 percent of people with high blood pressure got readings using the app that were in the normal range. The finding is concerning, because it means that many people with high blood pressure who use the app could be "falsely reassured" that they had normal blood pressure, the researchers said.

"We need to educate folks who have this app not to use it, and to be aware that there could potentially be apps out there that aren’t safe in the app store," said study researcher Dr. Timothy Plante, an internal medicine specialist at Johns Hopkins University School of Medicine.

Although the app, called Instant Blood Pressure, was removed from the iTunes app store last summer, it was previously one of the top 50 best-selling iPhone apps, and was downloaded at least 148,000 times, the researchers said. What's more, similar apps are still available in the app store. [The Best Heart Rate Monitor Apps]

Instant Blood Pressure was made by a company called AuraLife, was released in June 2014, and cost $3.99 to download. The app contained a disclaimer saying it was to be used for "entertainment purposes only" and was not an FDA-approved device. On the company's website today, it says the app is "not a replacement or substitute for a cuff or other blood pressure monitor."

But it appears that people are using the app for medical purposes — some people who have posted reviews of the app online have written that they had high blood pressure, and one reviewer even said they had a heart transplant, Plante said. "We know people are using it to self-manage serious blood-pressure-related conditions," Plante told Live Science.

In the new study, Plante and colleagues measured the blood pressure of 85 people, using both a standard blood pressure cuff and the Instant Blood Pressure app. To measure blood pressure using the app, Instant Blood Pressure says to place the top edge of the smartphone (near the microphone) onto the left side of the chest, and the index finger over the camera.

The study found that the app tended to underestimate high blood pressures, and overestimate low blood pressures. On average, the app was off by 12 mm Hg for systolic blood pressure (the top number in a blood pressure reading), and off by 10 mm Hg for diastolic blood pressure (the bottom number in a blood pressure reading.)

The Food and Drug Administration does regulate mobile apps, focusing on those that post a "greater risk to patients if they do not work as intended." The agency says it will regulate apps that "transform a mobile platform into a regulated medical device." For example, the FDA reviewed and cleared the Samsung S Health app, which measures heart rate, and the Withings Blood Pressure Monitor app, which goes along with that company's wireless blood pressure monitor.

Plante said the Instant Blood Pressure app seems to meet the criteria for an app that should be submitted for FDA review.

"Our study supports partnership of app developers, distributors and regulatory bodies to set and follow standards for safe, validated [mobile health] technologies," the researchers wrote in the March 2 issue of the journal JAMA Internal Medicine.

Ryan Archdeacon, Co-Founder & CEO, AuraLife, said "we welcome third party researchers taking an active interest in assessing our technologies," but said the study used the app in an unintended way. "Instant Blood Pressure is not a medical device and is not intended to diagnose disease, including hypertension," Archdeacon said in an email and in a statement. In addition, Archdeacon said that the Instant Blood Pressure app has undergone 18 updates since the study finished, which improved the app's algorithm and accuracy.

Archdeacon said that the app can be used to estimate changes in blood pressure within a single person, and so it can estimate the impact of certain activities — like meditation or breathing exercises — on blood pressure. (This claim was not tested by the study.)

"We share the authors’ concern at the idea of individuals, against the will of their physician, titrating their own therapies," Archdeacon told Live Science. "We believe such a public health concern can be tackled with education in and out of the clinic."

Follow Rachael Rettner @RachaelRettner. Follow Live Science @livescience, Facebook & Google+. Original article on Live Science.