A popular blood pressure app downloaded by thousands of people has been found to give wrong readings to hypertensive patients.

The smartphone app called "Instant Blood Pressure" made by AuraLife has been downloaded by thousands of people before it was taken off the app store. Scientists revealed that it gave inaccurate readings by saying they had normal blood pressure range when it was actually dangerously high. A study has been posted in the journal JAMA Internal Medicine.

"If Instant Blood Pressure worked, it would be a revolutionary new technology that would allow for low-cost screening and management of hypertension among smartphone users," said Dr. Timothy Plante of Johns Hopkins University, via CNBC.

"That it doesn't use a cuff is neat as folks don't generally like carrying around a bulky blood pressure monitor," Plante added by email. "Inaccurate measurements for high or low readings are concerning, however. Hypertension is known as the silent killer as it has an asymptomatic course that leads to serious conditions like heart disease, kidney disease, and stroke."

According to Reuters, the app works by placing the smartphone on the side of the chest to where the heart is while holding the right index finger over the device's camera.

The researchers tested it on 85 volunteers with a hypertension diagnosis. They checked their blood pressure twice and followed the instructions provided. They then compared the two readings. According to their study, the app had a tendency to give "normal blood pressure readings" when the volunteer's actual blood pressure was high.

"The low sensitivity for hypertensive measurements means that approximately four-fifths (77.5%) of individuals with hypertensive BP levels will be falsely reassured that their [blood pressure] is in the nonhypertensive range," the researchers wrote in their study.

Although the Instant Blood Pressure app is no longer online for purchase, it has been downloaded many times and still works on most smartphones. The researchers fear for the safety and health of those who are relying on it.

"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," Dr. Plante said, as reported by the Business Standard.

The researchers recommend using reliable and proven ways to get blood pressure readings through a trained medical professional.