The smartphone app can vibrate a drop of blood to determine the degree of coagulation–ScienceDaily

However, warfarin is not perfect. Patients should be examined frequently to ensure that the blood is in the correct range. Blood that is prone to coagulation can cause a stroke or heart attack, but blood that does not coagulate is possible. Bleeding will be prolonged after the injury. To be tested, the patient must go to the clinic or use an expensive home testing system.

Researchers at the University of Washington have developed a new blood clotting test that uses only a drop of blood and a smartphone’s vibration motor and camera. The system includes a plastic attachment that holds a small cup under the phone’s camera.

A person adds a drop of blood to a cup containing small copper particles and chemicals that initiate the blood clotting process. Then, while the camera monitors the movement of the particles, the vibration motor of the phone shakes the cup, slowing the movement of the particles and stopping when a blood clot is formed. Researchers have shown that this method is within the accuracy range of standard equipment in this field.

The team published these findings on February 11th. Nature Communications..

“At that time, doctors manually rocked the blood tube back and forth to monitor the time it took to form a blood clot, but this required a large amount of blood and could not be used at home. “Senior says. Author Shyam Gollakota, Professor UW of Paul G. Allen School of Computer Science & Engineering. “The creative leap here shows that by using the vibration motor of a smartphone, the algorithm can do the same, except for a drop of blood, and with the best technology on the market. Similar accuracy is obtained. “.”

Doctors can rank their blood clotting capacity using two numbers:

• The time it takes for a blood clot to form, known as “prothrombin time” or PT
• The ratio calculated from the PT makes it easier for doctors to compare results between different tests or laboratories. This is called the “international sensitivity ratio” or INR.

“Most people taking this drug take it for the rest of their lives. But this is not an unforgettable type. In the United States, most people are called the” desirable range “of PT / INR levels. It’s only in range. There is a 64% chance, “said Dr. Kelly Michaelsen, an assistant professor of anesthesiology and pain medicine at the Washington School of Medicine, co-author. “In countries with less frequent tests, such as India and Uganda, this number is even lower. How can we improve this? We need to allow people to test more often. And theirs. Take ownership of health care. “

Patients who can monitor PT / INR levels from home should only see a clinician if the test shows that they are out of the desired range, Michaelsen said.

Researchers wanted an inexpensive device that would work like a home blood glucose monitor for diabetics. A person can stab a finger and test a drop of blood.

“We started by vibrating a drop of blood and monitoring the waves on the surface,” said Justin Cheung, PhD student at Allen School at the University of Washington. “But it was really challenging with such a small amount of blood.”

The team added small copper particles. This is because tracking its movements is much more reliable.

“When the blood coagulates, it forms a tight network, and in the process, the particles bounce happily and no longer move,” Michaelsen said.

To calculate the PT and INR, the phone collects two time stamps. One is when the user inserts blood and the other is when the particles stop moving.

“For the first stamp, we’re looking for a user to insert a capillary tube containing a sample into the frame,” says Chan. “At the end of the measurement, look directly inside the cup and allow only the copper particles to move within those frames. The blood coagulates so quickly that the particles suddenly stop moving and between the frames. You can observe the difference. From there you can calculate the PT and map it to the INR. “

Researchers have tested this method with three different blood samples. As a proof of concept, the team started with plasma. Plasma is a component of blood that is clear and therefore easy to test. Researchers examined the plasma of 140 patients anonymized at the University of Washington Medical Center. The team also examined the plasma of 79 patients with known blood clotting problems. Under both of these conditions, the test results were similar to commercial tests.

Next, to mimic what patients at home experience, the team tested whole blood from 80 anonymized patients at both Harbor View and the University of Washington Medical Center. This test also yielded results that were within the accuracy range of the commercial test.

This device is still in the proof-of-concept stage. Researchers have published the code, exploring commercial opportunities and further testing. For example, all of these tests are currently done in the lab. The next step is to work with the patient to test this system at home. Researchers also want to see how the system works in more resource-constrained regions and countries.

“Almost every smartphone in the last decade has a vibration motor and a camera, which means that most people with a smartphone can use it. All they need is a simple plastic attachment. No additional electronics are needed, “says Gollakota. “This is the best in all the world. It’s basically the Holy Grail of the PT / INR test. It’s spartan and accessible to millions of people, even with very limited resources.”

Additional co-authors of this paper are Joanne Estergreen, Clinical Laboratory Supervisor, Clinical Laboratory Medicine and Pathology Department, UW School of Medicine, and Dr. Daniel Sabath, Professor of Laboratory Medicine and Pathology, UW School of Medicine. This study was funded by the Moore Foundation Fellowship.