UW scientists believe their at-home test could help more people on anticoagulants monitor their clotting levels and avoid blood clots
In a proof-of-concept study,researchers at the University of Washington (UW) are developing a new smartphone-based technology/application designed to enable people on anticoagulants such as warfarin to monitor their clotting levels from the comfort of their homes. Should this new test methodology prove successful, clinical laboratories may have yet one more source of competition from this at-home PT/INR test solution.
PT/INR (prothrombin time with an international normalized ratio) is one of the most frequently performed clinical laboratory blood tests. This well-proven assay helps physicians monitor clotting in patients taking certain anticoagulation medications.
However, the process can be onerous for those on anticoagulation drugs. Users of this type of medication must have their blood tested regularly—typically by a clinical laboratory—to ensure the medication is working effectively. When not, a doctor visit is required to adjust the amount of the medication in the bloodstream.
Alternatively, where a state’s scope of practice law permits, pharmacists can perform a point-of-care test for the patient, thus allowing the pharmacist to appropriately adjust the patient’s prescription.
Though in the early stages of its development, were the UW’s new smartphone-based blood clotting test to be cleared by the federal Food and Drug Administration (FDA), then users would only need to see a doctor when their readings went and stayed out of range, according to Clinical Lab Products (CLP).
The UW researchers published their findings in the journal Nature Communications, titled, “Micro-Mechanical Blood Clot Testing Using Smartphones.”
Enabling Patients to Test Their Blood More Frequently
More than eight million Americans with mechanical heart valves or other cardiac conditions take anticoagulants, and 55% of people taking those medication say they fear experiencing life-threatening bleeding, according to the National Blood Clot Alliance.
They have reason to be worried. Even when taking an anticoagulation drug, its level may not stay within therapeutic range due to the effects of food and other medications, experts say.
“In the US, 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. We need to make it easier for people to test more frequently,” said anesthesiologist and co-author of the study Kelly Michaelsen, MD, PhD, UW Assistant Professor of Anesthesiology and Pain Medicine, in a UW news release.
How UW’s Smartphone-based Blood Clotting Test Works
The UW researchers were motived by the success of home continuous glucose monitors, which enable diabetics to continually track their blood glucose levels.
According to the Nature Communications paper, here’s how UW’s “smartphone-based micro-mechanical clot detection system” works:
- Samples of blood plasma and whole blood are placed into a thimble-size plastic cup.
- The cup includes a small copper particle and thromboplastin activator.
- When the smartphone is turned on and vibrating, the cup (which is mounted on an attachment) moves beneath the phone’s camera.
- Video analytic algorithms running on the smartphone track the motion of the copper particle.
- If blood clots, the “viscous mixture” slows and stops.
- PT/INR values can be determined in less than a minute.
“Our system visually tracks the micro-mechanical movements of a small copper particle in a cup with either a single drop of whole blood or plasma and the addition of activators,” the researchers wrote in Nature Communications. “As the blood clots, it forms a network that tightens. And in that process, the particle goes from happily bouncing around to no longer moving,” Michaelsen explained.
The system produced these results:
- 140 de-identified plasma samples: PT/INR with inter-class correlation coefficients of 0.963 and 0.966.
- 79 de-identified whole blood samples: 0.974 for both PT/INR.
Another At-home Test That Could Impact Clinical Laboratories
The UW scientists intend to test the system with patients in their homes, and in areas and countries with limited testing resources, Medical Device Network reported.
Should UW’s smartphone-based blood-clotting test be cleared by the FDA, there could be a ready market for it. But it will need to be offered it at a price competitive with current clinical laboratory assays for blood clotting, as well as with the current point-of-care tests in use today.
Nevertheless, UW’s work is the latest example of a self-testing methodology that could become a new competitor for clinical laboratories. This may motivate medical laboratories to keep PT/INR testing costs low, while also reporting quick and accurate results to physicians and patients on anticoagulants.
Alternatively, innovative clinical laboratories could develop a patient management service to oversee a patient’s self-testing at home and coordinate delivery of the results with the patient’s physician and pharmacist. This approach would enable the lab to add value for which it could be reimbursed.
—Donna Marie Pocius