Debbie Cohen, MD, director of the Clinical Hypertension Program at Penn Medicine, doesn’t mince words when talking about the smartphone apps and kiosks in malls and pharmacies that take blood pressure.
“People shouldn’t be using them,” said Cohen, who laid out the shortcomings and dangers of the technologies in a recent commentary in the Journal of Clinical Hypertension. “The readings can be completely inaccurate.”
One recent study she cites shows just how inaccurate they can be. An app, which has since been removed, was off by up to 15 mm Hg for both systolic and diastolic readings compared to the standard blood pressure instrument, known as a sphygmomanometer, researchers from Johns Hopkins University found. That’s a significant enough difference to cause worry.
In fact, almost 80 percent of people with levels in the hypertension territory (anything above 140 over 90 is considered high blood pressure) would be falsely reassured that their levels were within normal range if they used the app, Cohen and her co-author, Raymond R. Townsend, MD, director of Penn’s Hypertension Program, argue in the piece.
They join a growing chorus of researchers who have taken a more critical eye to the smartphone health apps market over the last several years. Apps disappear from mobile stores after studies questioning their validity surface, but it’s a bit of a whack-a-mole game, so more will eventually pop up. Some of the blood pressure apps even sit in the Apple Store’s top 25 apps list for months.
They’re easy to use, after all, and the experiment seems intriguing. Place a finger on the camera of the iPhone and press another on the screen, one app’s directions read.
I decided to try it.
After 30 seconds, my blood pressure reading appeared on the screen: 111 (systolic) over 71 (diastolic). That’s a relief, I thought, since those numbers put me in the “normal” blood pressure column. Still, was it right? No.
A call to my doctor’s office, where a nurse had taken my blood pressure not too long ago the old-fashioned way, with a sphygmomanometer, revealed a different number: 100 over 78.
“That is a difference, but it’s not a crazy difference,” Cohen said. Both of those readings, she said, are considered normal, so it’s not likely to send me down any dangerous paths. But what if a person was up in the 130 or 150 range, and their reading was off by 11 mm Hg? It could give someone a false sense of security or set off a false alarm. They could end up altering their medications or stop screenings, she said.
“I think the danger is the interpretation of the data,” Cohen said. “If you get a reading and you think your blood pressure is well controlled, you run the risk of being undertreated. Or the reverse: you think your pressure is really high, and based on that, there is overtreatment.”
Even with medications available to control it, high blood pressure remains a “silent killer” in the United States that affects a large portion of the population. That’s why clinicians recommend some patients to monitor their blood pressure at home, and to share that info with clinicians to help guide treatment decisions, Cohen said.
The home monitors may be more expensive than an app, which are often free, but they’re still relatively affordable and easy to access. Stores such as Walmart and Amazon.com sell automated blood pressure monitors and, in some cases, insurance companies will cover the costs.
“Self-monitoring blood pressure definitely helps improve outcomes, and we really encourage that, but using a methodology that is not validated is really a waste of time,” she said. “You shouldn’t make any clinical decision based on it.”
Kiosks are a problem, too, because they are not standardized and rarely calibrated, the authors said. Appropriate cuff sizes are also often unavailable, leading to falsely high readings if the cuff is too small, and low readings if it’s too big.
“Without longitudinal data showing the value of these apps or kiosks…practitioners cannot provide sensible, informed advice to patients regarding these devices, and their use should not be encouraged,” they wrote.
What also alarms Cohen is the lack of involvement from the research community. Less than five percent of blood pressure apps were developed with academic input, she said, and the literature shows that they work poorly.
A 2015 report from the IMS Institute for Healthcare Informatics puts the number of available health and wellness apps at 165,000, but that was two years ago, so many more have likely been added. What hasn’t changed is that most don’t need U.S. Food and Drug Administration approval to ensure their effectiveness or safety.
Clinically proven blood pressure apps certainly aren’t out of reach, Cohen said, but it will take more oversight and collaboration from both researchers and the Association of for the Advancement of Medical Instrumentation (AAMI), an organization that set standards for medical technology, to make that happen.
“If they all worked together, they could honestly have a huge role in developing these apps,” she said. “But we’re not there yet.”