FYI. Ask your doctor if this is for you.
At-home Blood Clot Test Requires Only a Smartphone
Blood clots form naturally in the human body as a way to stop bleeding if injured, but for those who have heart conditions or have had heart attacks/strokes in the past, blood clots are dangerous. That’s why more than 20 million Americans take warfarin, the most prescribed blood-thinning medication in the U.S.
But, warfarin is not the end-all-be-all. While it is extremely effective, it does require patients to be tested frequently to ensure their blood is in the correct “range.” To be tested, patients either have to go to a clinic laboratory or use a costly at-home testing system.
“Most people taking this medication are taking it for life. But this is not a set-and-forget type of thing—in the U.S., most people are only in what we call the desirable range about 64% of the time," said co-author Dr. Kelly Michaelsen, assistant professor of anesthesiology and pain medicine in the UW School of Medicine. "This number is even lower—only about 40% of the time—in countries such as India or Uganda where there is less frequent testing. How can we make this better? We need to make it easier for people to test more frequently and take ownership of their health care."
Building off that idea, and taking a cue from at-home blood sugar monitors for diabetics, Michaelsen and her team at the University of Washington developed a proof-of-concept, at-home testing platform that only needs two common elements: a single drop of blood and a smartphone that vibrates and takes pictures.
The designed testing platform includes a plastic attachment that holds a tiny cup beneath the phone's camera. A person adds a drop of blood to the cup, which contains a small copper particle and a chemical that starts the blood-clotting process. Then, the phone's vibration motor shakes the cup while the camera monitors the movement of the particle, which slows down and then stops moving as the clot forms.
The scientists developed to system to mimic the two ways in which doctors rank blood-clotting ability. One number is the prothrombin time (PT), or the time it takes for the clot to form, while the second is the international normalized ratio (INR), which is a ratio calculated from the PT that allows doctors to more easily compare results between different tests and/or laboratories.
To calculate PT and INR, the phone collects two time stamps: one when the user inserts the blood and the second when the particle stops moving.
“For the first time stamp, we're looking for when the user inserts a capillary tube containing the sample in the frame," said lead author Justin Chan, a UW doctoral student. “For the end of the measurement, we look directly at the interior of the cup so that the only movement within those frames is the copper particle. The particle stops moving abruptly because blood clots very quickly, and you can observe that difference between frames. From there we can calculate the PT, and this can be mapped to INR.”
In their study, published in Nature Communications, the scientists tested the platform on three different types of blood samples. They first tested plasma from 140 anonymized patients at the University of Washington Medical Center. They then examined plasma from 79 patients with known blood-clotting issues. To mimic what a patient at home would experience, the team also tested whole blood from 80 anonymized patients.
The results demonstrated that the platform falls within the accuracy range of the standard instruments of the field, as well as commercial tests, for all three types of blood samples.
“Back in the day, doctors used to manually rock tubes of blood back and forth to monitor how long it took a clot to form. This, however, requires a lot of blood, making it infeasible to use in home settings,” said senior author Shyam Gollakota, UW professor of engineering. “The creative leap we make 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.”
As all the current tests have been performed in the lab, the research team says the next step is to work with patients to test the system at home. After that, the team wants to see how the system fares in resource-limited areas and countries.
In the meantime, the scientists have publicly released the code for the platform and are exploring commercialization opportunities.
Photo: Researchers at the University of Washington have developed a new blood-clotting test that uses only a single drop of blood and a smartphone vibration motor and camera. The system includes a plastic attachment that holds a tiny cup of blood beneath the phone's camera. Credit: Mark Stone/University of Washington
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