Study in 85 volunteers found inaccurate measurements, researchers say

A popular smartphone app purported to accurately measure blood pressure simply by placing a cellphone on the chest with a finger over the built-in camera lens misses high blood pressure in eight out of 10 patients, according to research from Johns Hopkins.

Although the app, called Instant Blood Pressure, is no longer available for purchase, it was downloaded more than 100,000 times and is still functional on phones, the researchers say.

“We think there is definitely a role for smartphone technology in health care, but the results of our study speak to the need for scientific validation and regulation of these apps before they reach consumers,” says Timothy B. Plante, M.D., a fellow in the Division of General Internal Medicine at the Johns Hopkins University School of Medicine.

The study, described at the American Heart Association’s Epidemiology and Lifestyle meeting and concurrently online March 2 in JAMA Internal Medicine, was conducted by Plante and Seth Martin, M.D., M.H.S., an assistant professor in the Division of Cardiology at the Johns Hopkins University School of Medicine.

Blood pressure is best measured, the researchers say, using the well-established technique of inflating a cuff attached around the brachial artery in the arm to detect the force of blood flowing when the heart is beating and at rest. Either a trained medical professional or a machine “listens” to sounds from the brachial artery as blood flows under variable pressure from the cuff.

To test the app’s method of measuring blood pressure, Martin, Plante and colleagues recruited 85 adult volunteers among patients and staff members in clinics associated with Johns Hopkins Medicine. The participants self-reported a range of body mass measurements, races and ethnicities, all factors known to influence blood pressure.

Each participant had his or her resting blood pressure measured twice using a reliable automated blood pressure monitor commonly used in research studies to avoid measurer variation or error. Participants also used the app to measure their own blood pressure twice on the same day.

Results showed close to 80 percent of study participants with clinically high blood pressure, defined as 140/90 millimeters of mercury or above as measured by the automated blood pressure monitor, showed normal blood pressure with the app.

The authors say that it is unclear how the app arrives at a blood pressure number.

Martin and Plante note that mobile health smartphone applications are becoming more commonplace, and many have the potential to greatly improve health by putting personalized medical resources and information literally in the hands of patients through cellphones.

“The next big step in health care is to further engage folks in their own care and motivate them to reduce risks associated with diseases like high blood pressure,” Plante says. “But care must be taken to make sure they get the accurate ways to do that.”

 Other researchers who participated in this study include Bruno Urrea, M.D.; Roger S. Blumenthal, M.D.; Edgar R. Miller III, M.D., Ph.D.; and Lawrence J. Appel, M.D., M.P.H., all of Johns Hopkins, and Zane T. MacFarlane, of Pomona College.

The work was funded by the PJ Schafer Cardiovascular Research Fund.

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