Clopidogrel (Plavix) is a medicine to prevent blood clots, which can cause heart attacks and strokes. It may be prescribed after a heart attack, after angioplasty, and for people who have coronary artery disease or peripheral arterial disease.

Some people have changes, or mutations, to a certain gene (CYP2C19). These changes may keep the body from being able to use clopidogrel to prevent blood clots. If a person with these genetic changes takes clopidogrel, the medicine may not work. This may raise the person's chance of having a heart attack or a stroke.

A genetic test might be used if your doctor thinks that your body is not using clopidogrel properly. This test checks to see if you have genes that let your body use this medicine. But experts aren't yet sure whether genetic changes keep clopidogrel from preventing a heart attack or stroke. This genetic test alone is not enough to tell whether the medicine will help you. You also may have a test that shows how your body' s platelets are working to clot blood. Having a platelet test after you take an antiplatelet can show if the medicine is working.

The test is done by swabbing the inside of your cheek.