Although platelets are needed to produce clots at injury sites, they also play a role in the progression of Vascular Disease. Today, the treatment of Coronary Artery Disease (CAD) with platelet aggregation inhibitors (antiplatelet drugs) which help to prevent the formation of potentially harmful blood clots has become a cornerstone of cardiovascular medicine. Aspirin and clopidogrel have emerged as critical therapies in the treatment of cardiovascular disease.

CAD patients are in need for primary and secondary prevention and are using aspirin on a daily basis. Approximately 14 million Americans have CAD and each year 1.2 million people develop the most deadly presentation of CAD, acute myocardial infarction (AMI), of which 500,000 die.

Many individuals treated with aspirin do not achieve the inhibitory response anticipated, a phenomenon termed "aspirin resistance". A significant correlation was found between aspirin resistance as measured by platelet aggregation and the composite primary outcome of death, myocardial infarction, or cerebrovascular accident in patients with stable cardiovascular disease. Thus, the need to diagnose aspirin and clopidogrel resistance in patients and prevent future cardiovascular events is an increasing priority in the medical community. Unfortunately, there is no one test that provides comprehensive evaluation of platelet function, nor is there widespread agreement on which test(s) are best for each circumstance.