Aspirin is the most commonly prescribed drug and the most cost effective therapy. However treatment failure has been of great concern in clinical practice. In the laboratory, assessment of platelet responsiveness to aspirin is not required routinely but due to some clinical reasons the test is indicated. It is important for the laboratory to have the appropriate procedure to perform the test as well as to interpret the results. Whole blood platelet aggregation method with conventional platelet aggregometer is able to detect the aspirin resistance state and it is less laborious than using...