New calculator better predicts stroke risk
Created by Carolina’s Dr. Samuel Short, the improved tool helps physicians decide if atrial fibrillation patients should take blood thinners.
Researchers at the UNC School of Medicine and the University of Vermont have developed a more precise way to assess stroke risk in people with atrial fibrillation, a condition that affects 10.5 million Americans and is a leading cause of stroke.
Their findings, published in the Journal of Thrombosis and Haemostasis, show that adding blood tests to an existing risk calculator can help physicians better determine who truly needs blood thinners — powerful drugs that prevent strokes but can also cause dangerous bleeding.
“This will help doctors better select patients for anticoagulation, potentially saving lives and reducing health care costs,” said Dr. Samuel Short, a first-year hematology and oncology fellow at the UNC School of Medicine and lead author of the paper.
Short began this research as a medical student at the University of Vermont’s Larner College of Medicine alongside faculty mentor Dr. Mary Cushman. Together, they used data from an ongoing national cohort study of 30,239 adults monitored for stroke and related diseases termed Reasons for Geographic and Racial Differences in Stroke.
Atrial fibrillation is the most common arrhythmia that makes the top chambers of the heart quiver instead of pumping normally. The blood inside the heart moves more slowly, and this pooling of blood can lead to blood clots.
“Blood clots can be ejected by the heart to the brain — causing stroke,” said Short. “Blood thinning medicines, or anticoagulants, make it harder for the blood to clot, lowering stroke risk. However, not every patient can or should be on a blood thinner.”
Blood thinners can reduce stroke risk for some people with atrial fibrillation, but some people who take them experience a breakthrough stroke anyway, with the medications potentially causing dangerous side effects related to uncontrolled bleeding.
Stroke risk calculators aren’t exactly new. Physicians currently use a conventional risk calculator that considers a patient’s age, sex and medical history to estimate a patient’s stroke risk before prescribing anticoagulants.
However, the conventional risk calculator does not account for heart dysfunction, accelerated blood clotting and inflammation, which are all important risk factors for stroke.
“Current calculators are not particularly accurate and improving these tools can both decrease strokes and bleeding by offering the right medicines to the right patients,” said Short.
The improved risk calculator accounts for these additional risk factors by adding results from the blood tests to the calculation. The calculator is based on two studies led by Short, Cushman and other researchers at the University of Vermont, which were published in the Journal of Thrombosis and Haemostasis.
In the first study, researchers looked at nine blood tests that might predict the occurrence of stroke in 713 people who were taking an anticoagulant to prevent stroke. With a 12-year follow-up, 9% of these people developed a breakthrough stroke. Short and Cushman discovered that three blood test results identifying proteins associated with heart dysfunction, accelerated clotting and inflammation activity were linked to the risk of a stroke.
In the second study, researchers looked at the same 9 blood tests in 2,400 people who were not taking an anticoagulant to prevent stroke. Over 13 years, 7% of them developed a stroke. Short and Cushman discovered that two of the blood tests increased the ability to predict a stroke.
The researchers used these two blood tests to create a more accurate risk scoring system. This improved scoring system can be used by clinicians to decide which patients with atrial fibrillation might benefit the most from anticoagulant medication.
Although the calculator is not yet ready for use in clinics, physicians can use the new improved stroke risk calculator online for easy access.
