Several studies have concluded that 5-40% of individuals who take aspirin every day to help prevent heart attacks and strokes may not benefit from the anticoagulant effect of aspirin. A person is considered aspirin-resistant if:
- The individual is using aspirin therapeutically (75-150 mg/day), and an ischemic cardiac event occurs
- Laboratory testing determines a lack of antiplatelet effect despite therapeutic dosing for at least five days
An algorithm, such as the one shown on the following page, may be a useful tool for determining whether platelet function testing should be ordered.
