Smart talk app

Smartphone app can measure clotting from a drop of blood and could ‘prevent millions of heart attacks’

SEATTLE— An app that uses cellphone vibrations to measure blood clotting could prevent millions of life-threatening heart attacks. According to scientists, the technology offers people taking heart medication a much cheaper way to monitor their blood thickness.

Although blood clots form naturally to prevent bleeding when a person is injured, they can also be fatal for patients with heart disease. People with a mechanical heart valve could be particularly at risk of suffering a stroke or heart attack if their blood thickens. That’s why millions of people living with heart problems around the world rely on blood-thinning tablets like warfarin to keep it from clotting.

Maintaining the right level of thickness, however, is tricky and requires patients to get tested regularly. Typically, this is done either at a medical clinic or using an expensive home test kit. Now researchers at the University of Washington have found a much “smarter” solution. using a cell phone.

“Back then, doctors used to manually shake blood tubes back and forth to monitor how long it took for a clot to form,” says lead author Shyam Gollakota, a professor at the Paul G. Allen School of Computer Science & Engineering at the university, in a statement. “This, however, requires a lot of blood, which makes it impossible to use at home.”

UW researchers have developed a new blood clotting test that uses just a single drop of blood and a smartphone with a plastic attachment that holds a small cup under the phone’s camera (pictured here). Note: This photo simulates the operation of this system, and the “blood” shown here is not real. (Credit: Mark Stone/University of Washington)

Their new system contains a small cup under the phone’s camera that contains a small copper particle and a chemical to start the blood clotting process. Once a drop of blood has been added, the phone’s motor vibrates, shaking the cup as the camera tracks the particle’s movements. As the blood gets thicker and thicker, the particle slows down and eventually stops once a clot has formed.

The phone then records two timestamps, one when the drop of blood is added and the second when the particle stops moving. This way it can measure the time it takes for blood to clot, which is either measured by something called prothrombin time (PT) or an international normalized ratio (INR).

“The creative leap we’re making here is that we’re showing that by using the vibration motor on a smartphone, our algorithms can do the same thing, except with a single drop of blood,” Gollakota says. “And we get accuracy similar to the best commercially available techniques.”

Their new technology could help millions of people who depend on blood-thinning drugs like warfarin keep tabs on their clotting abilities.

“Most people who take this drug take it for life,” notes co-author Dr. Kelly Michaelsen, assistant professor of anesthesiology and pain medicine at the UW School of Medicine. “But it’s not a set-it-and-forget-it thing – in the US, most people are only in what we call the ‘desirable range’ of PT/INR levels about 64% of the time. That number is even lower – only around 40% of the time – in countries like India or Uganda where testing is less frequent.

“How can we make this better? We need to empower people to get tested more frequently and take ownership of their healthcare.”

Using their technology, patients would only need to visit a clinic if their results fell outside of the desirable range. Their device was tested on three different types of blood samples from 140 anonymized patients at the university’s medical center. They also looked at 79 patients with known blood clotting problems and found the results to be equivalent to other commercially available tests.

While the device is still in the proof-of-concept stage, researchers have made the application code and explore next steps. They would like to further test the system in people’s homes and in countries with fewer resources.

“Almost every smartphone of the last decade has a vibration motor and a camera,” says Gollakota. “That means almost anyone with a phone can use it. All you need is a simple plastic attachment, no extra electronics of any kind. It’s the best of all worlds – it’s basically the holy grail of PT/INR testing.”

The results are published in the journal Nature Communication.

South West News Service writer Tom Campbell contributed to this report.