Warfarin is an anti-coagulant prescribed to people with various heart conditions and those who have experienced or are at high risk for a blood clot. Anti-coagulants are also referred to as “blood thinners” as they reduce blood clotting potential. About two million Americans take warfarin, and these patients require regular blood tests to monitor the effects of the drug. Doctors measure prothrombin time (PT) and international normalized ratio (INR), and these tests are cumbersome and expensive. Testing is done in a laboratory setting with expensive point-of-care equipment.
Researchers from the University of Washington recently developed a testing system that uses a smartphone vibration motor and camera to track movements on a copper particle. The system can detect how well blood will clot from a single drop of blood. The research team recently published the results of this proof-of-concept study in Nature Communications.
The testing system contains a plastic attachment that connects a cup to the smartphone. The cup is situated under the smartphone camera. Inside the cup is a copper particle and a small amount of tissue factor, a chemical that initiates the blood clotting process. The patient adds a drop of blood to the cup, and the smartphone’s vibration motor shakes the copper particle. The camera captures the movement of the particle to calculate clotting time. The particle vibrates quickly when blood is in a liquid (not clotted) state. As the blood clots, the particle’s ability to move is restrained. A video processing algorithm can then compute the PT and INR values.
Compared to the standard point-of-care blood testing done at a hospital laboratory, 99.6% of plasma measurements and 100% of whole blood measurements fell within the allowable error for INR testing. While these data are extremely promising, the authors note that additional studies are necessary to ensure the performance of this blood testing system works in at-home settings.
The results of this study demonstrate a major step towards providing necessary medical tests at low cost from the comfort of a patient’s own home. Further manipulation of this testing system could perfect the testing of additional blood measurements. Successful implementation of this technology could reduce costs and increase access to care.