The test uses a smartphone's built-in vibration motor and camera to track movement of a copper particle in a drop of blood.
The developers will present the results of a study that describes their work on Wednesday in a Scientific Poster Session at AACC 2022.
The group tested blood from 140 anonymous patients at the University of Washington Medical Center in addition to blood from 79 patients with known blood-clotting issues.
In both groups, the new test produced results similar to those of laboratory PT/INR tests.
As a next step, Michaelsen is planning to research whether patients can use the new test by themselves at home. She envisions it being helpful for people in rural areas to minimize long and increasingly expensive trips to doctors.
The aim is to develop a test that will lead to more people spending more time in the desirable PT/INR range, which would mean they are not at risk for clots or uncontrolled bleeding.
People who take the blood-thinning medication warfarin to prevent blood clots that can lead to heart attacks need frequent blood testing to ensure that the drug is working. Currently, this testing occurs in a clinical laboratory or using expensive at-home testing systems; it involves a particular measure of the time it takes for a clot to form, PT, and calculating the INR so doctors can compare results between different tests or laboratories.