People are often told to take low-dose aspirin to reduce the risk of heart attacks and stroke. But that preventive remedy doesn't work for a lot of people.
Researchers say they've found genetic variations that might be used to identify people who don't respond well to aspirin. If the results prove out, there could soon be a blood test to tell who benefits from aspirin, and who needs to look for other treatments to reduce cardiovascular risk.
Aspirin is prescribed because it makes the blood's platelets less sticky, and less apt to clump together and form blood clots. Clots are a key cause of both heart attacks and strokes.
But it's become clear that that remedy doesn't work for everyone. Anywhere from 10 to 30 percent of people may not get any protective benefit from aspirin, according to studies.
There are tests to tell how aspirin affects platelets, but they need to be done within a few hours after blood is drawn, and involve some tricky lab work. So they're not practical as a screening test for the millions of people who take aspirin to prevent heart attacks and stroke.
To find out if there's a better way to identify those people, researchers at Duke University Medical Center gathered up two groups healthy volunteers who took 325 milligrams of aspirin every day for up to a month, and people with heart disease who already were taking low-dose aspirin (81 mg) as part of their treatment.
They then tested how well the people's blood platelets responded to the aspirin, and tested the people's genes.
They found 60 genes that were active in people, healthy and not, who didn't respond well to the aspirin. Their platelets stayed sticky.
The researchers then looked for those 60 genes in people who had had cardiac testing at the Duke hospital. They found that same genetic signature in patients who later had heart attacks or died, even if they were taking aspirin.
"Potentially you could take this 60 gene-set signature and develop some sort of diagnostic test, without all the time constraints current tests have," says Dr. Deepak Voora, an assistant professor of medicine at Duke and lead author of the study.
It's not clear what could help people who don't respond to aspirin, Voora says. It may be a question of figuring out different doses of aspirin for different people. Or it could be that they would need a different drug that inhibits platelet clotting, such as clopidogrel (Plavix) or similar medications.
The article was published online Wednesday in The Journal of the American College of Cardiology.