University of Washington researchers develop clinical lab test for blood clotting that uses a smartphone and a single drop of blood

UW scientists believe their home test could help more people taking anticoagulants to monitor their clotting levels and prevent blood clots

In a proof-of-concept study, University of Washington (UW) researchers are developing a new smartphone-based technology/application designed to allow people taking anticoagulants such as warfarin to monitor their clotting levels from the comfort of their home. to check. Should this new testing methodology prove successful, clinical labs may have another source of competition from this home PT/INR testing solution.

PT/INR (prothrombin time with an international normalized ratio) is one of the most commonly performed clinical laboratory blood tests. This proven test helps doctors check clotting in patients taking certain anticoagulants.

However, the process can be stressful for people taking anticoagulants. Users of this type of medication should have their blood tested regularly, usually by a clinical lab, to make sure the medication is working effectively. If not, a doctor’s visit is needed to adjust the amount of medication in the bloodstream.

Alternatively, where the scope of a state’s practice permits, pharmacists may perform a patient point-of-care test, which allows the pharmacist to appropriately adjust the patient’s prescription.

Although in the early stages of its development, the UW’s new smartphone-based blood-clotting test had to be approved by the federal Food and Drug Administration (FDA), users would only need to see a doctor when their readings went and stayed out of range, according to Clinical Lab ProductsCLP

The UW researchers published their findings in the journal nature communicationtitled: “Micro-Mechanical Blood Clot Tests With Smartphones.”

Enabling patients to test their blood more often

More than eight million Americans with mechanical heart valves or other heart conditions take anticoagulants, and 55% of people taking those drugs say they fear life-threatening bleeding, according to the National Blood Clot Alliance.

They have reason to worry. Even when taking an anticoagulant drug, the level may not stay within the therapeutic range because of the effects of food and other drugs, experts say.

“In the US, most people are only in what we call the ‘desired range’ of PT/INR levels about 64% of the time. This number is even lower – only about 40% of the time – in countries like India or Uganda, where testing is less frequent. We need to make it easier for people to test more often,” said anesthetist and study co-author Kelly Michaelsen, MD, PhD, UW assistant professor of anesthesiology and pain medicine, in a UW news release.

“In the past, doctors would manually rock blood tubes back and forth to check how long it took for a clot to form. However, this requires a lot of blood, making it unfeasible to use at home,” said senior study author. Shyam Gollakota, PhD (above), professor and head of the Networks and Mobile Systems Lab at UWs Paul G. Allen School of Computer Science and Engineering, in the UW press release. “The creative leap we’re taking here is 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 an accuracy comparable to the best commercially available techniques [used by clinical laboratories]† (Photo copyright: University of Washington.)

How UW’s smartphone-based blood clotting test works

The UW researchers were motivated by the success of continuous home glucose meters, which allow diabetics to continuously monitor their blood glucose levels.

According to the nature communication paper, here’s how UW’s “smartphone-based micromechanical clot detection system” works:

  • Blood plasma and whole blood samples are placed in a thimble-sized plastic cup.
  • The cup contains a small copper particle and thromboplastin activator.
  • When the smartphone is on and vibrating, the cup (which is attached to an attachment) moves under the phone’s camera.
  • Video analysis algorithms running on the smartphone track the movement of the copper particle.
  • As blood clots, the “viscous mixture” slows down and stops.
  • PT/INR values ​​can be determined in less than a minute.

“Our system visually tracks the micromechanical movements of a small copper particle in a cup containing either a single drop of whole blood or plasma and the addition of activators,” the researchers wrote in Nature Communication. “As the blood clots, it forms a network that tightens. And in that process, the particle goes from happily bouncing to no longer moving,” Michaelsen explained.

The system produced these results:

  • 140 unidentified plasma samples: PT/INR with correlation coefficients between classes of 0.963 and 0.966.
  • 79 anonymized whole blood samples: 0.974 for both PT/INR.

Another home test that could affect clinical labs

The UW scientists plan to test the system in patients’ homes and in areas and countries with limited testing resources, Medical Device Network reported.

Should UW’s smartphone-based blood clotting test be approved by the FDA, there could be a market for it. But it must be offered at a price that is competitive with current clinical laboratory blood clotting tests, as well as with current point-of-care tests in use today.

Nevertheless, UW’s work is the latest example of a self-test method that could become a new competitor for clinical labs. This can motivate medical labs to keep the cost of PT/INR testing low, while also reporting fast and accurate results to physicians and patients taking anticoagulants.

Alternatively, innovative clinical labs could develop a patient management service to monitor a patient’s home self-tests and coordinate delivery of results with the patient’s physician and pharmacist. This approach would allow the lab to add value for which it could be remunerated.

Donna Marie Pocius

Related information

Smartphone app can vibrate a single drop of blood to determine how well it clots

Blood clotting tests with smartphones

Micromechanical blood clot testing with smartphones

55% of Americans on blood thinners say they fear serious bleeding, 73% more cautious about routine activities to avoid risks

University of Washington develops new blood clotting test

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