A popular smartphone app is not as accurate as it claims to be. A Johns Hopkins study has found that the app, Instant Blood Pressure, which is no longer available for download, could not measure high blood pressure correctly in 80 percent of the cases.

The team headed by Timothy B. Plante and Seth Martin had recruited 85 adult volunteers who were either patients or staff members at clinics that were associated with Johns Hopkins Medicine to test out the app.

The participants' resting blood pressure levels were recorded twice using an automated blood pressure monitor. The participants were then asked to use the Instant Blood Pressure app twice throughout the same day. The team found that the app failed to record accurate blood pressure levels in eight out of 10 participants.

The researchers noted that people who had purchased the app for $4.99 and still have it on their phones should not continue to use it. Since high blood pressure increases the risk of several health conditions, such as heart attack and stroke, not being aware of how high your levels are can be life threatening.

"Because this app does such a terrible job measuring blood pressure, it could lead to irreparable harm by masking the true risk of heart attacks and strokes in people who rely on the accuracy of this information," Plante, a fellow in the Division of General Internal Medicine at the University, said in the press release. "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. But care must be taken to make sure they get the accurate ways to do that."

He added, "Going forward, we need to make sure regulatory bodies and app stores and developers are doing rigorous validation studies before they [new blood pressure monitoring apps] are released. If a blood pressure cuff needs to be cleared by the FDA, then an app for blood pressure should, too."

The study, presented at the American Heart Association's Epidemiology and Lifestyle meeting, was published in JAMA Internal Medicine.