Laboratory analysis of response to aspirin and/or clopidogrel therapy can play an important role in monitoring patients at high risk for adverse cardiac events. This section of the course will discuss different analytic methodologies, some which can be utilized for both asprin resistance testing and clopidogrel resistance testing, and others that are unique to aspirin or clopidogrel testing. Examples of the test methods which will be discussed include: optical light transmission analysis, whole blood impedance aggregometry, Helena Laboratories PlateletWorks Kits, and cartridge-based platelet aggregation testing.
One of the main test methods available to analyze aspirin or clopidogrel resistance is through platelet aggregation in vitro. This method measures platelet function and determines aspirin or clopidogrel response based on clotting time results. Agonists are used. Platelets with impaired functionality result in increased clotting times. If the sample does not show the inhibition of platelet aggregation formation within the reference intervals defined for aspirin or clopiogrel therapy, the individual may have a lessened response or be unresponsive to therapy. We will compare various methods that utilize this principle in upcoming course pages.