Making waves: vibrating smartphone app developed to determine clotting effectiveness in blood samples

16 Feb 2022

Written by Amy White

Researchers at the University of Washington (WA, USA) have created a new blood-clotting test that only requires a single drop of blood and a smartphone vibration motor and camera.

Blood clots form naturally to stop bleeding when injured. However, for millions of individuals, medical conditions such as atrial fibrillation, mechanical heart valves and genetic mutations, increase the risk of mortality from complications related to blood clotting. These individuals require lifelong administration of blood-thinning medication such as warfarin, an effective treatment, however, also one of the most common causes of hospitalization due to adverse drug events. Hence, adverse effects must be closely monitored via frequent prothrombin time (PT) or international normalized ratio (INR) tests to assess coagulation due to the drug’s narrow therapeutic index and interactions with food and other medications. These tests must be done either in a clinical setting or at home utilizing costly testing systems.

Shyam Gollakota, Professor in the University of Washington’s Paul G Allen School of Computer Science & Engineering, commented:

“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…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. And we get accuracy similar to the best commercially available techniques.”

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Individuals can add a drop of blood to the cup, which contains a small copper particle along with other chemicals that begin the blood-clotting process. The individual’s own smartphone vibration motor shakes the cup while the camera monitors the movement of the particle, which slows down as the clot forms. Researchers have suggested this method falls within the accuracy range of the standard instruments of the field.

Kelly Michaelsen, Assistant Professor of anesthesiology and pain medicine at the University of Washington School of Medicine, stated:

“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’ of PT/INR levels about 64% of the time…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.”

The study researchers wanted to create an inexpensive device that could function closely to how at-home blood sugar monitors function for people with diabetes, wherein a patient can prick their finger to test a drop of blood.

Michaelsen further added:

“This would mean that patients who can monitor their PT/INR levels from home would only need to go to see a clinician if the test suggested they were outside of that desirable range,”

Given the universal usage of smartphones globally, this proof-of-concept technology may provide inexpensive and useful PT and INR testing in low-resource environments.

Sources: Chan J, Michaelsen K, Estergreen J K, Sabath D E & Gollakota S. Micro-mechanical blood clot testing using smartphones. Nature. Com. 13, 831 (2021). University of Washington press release www.washington.edu/news/2022/02/11/smartphone-app-vibrate-single-drop-of-blood-determine-how-well-clots/