Laboratory evaluation of clopidogrel responsiveness by platelet function and genetic methods.

Clopidogrel is a widely used antiplatelet agent that irreversibly inhibits platelet P2Y12 ADP receptors after conversion to an active metabolite. There are a number of laboratory tests capable of detecting clopidogrel-induced platelet inhibition and published literature correlates suboptimal clopidogrel response to adverse cardiovascular outcomes. Genetic polymorphisms are thought to affect conversion of the prodrug to the active metabolite, and the FDA has recently added a black-box warning to clopidogrel to highlight the effects of these polymorphisms on drug bioavailability and to inform prescribers about the availability of genetic testing. For these reasons, there is growing interest in the use of laboratory tests to monitor patients treated with clopidogrel. This article summarizes the currently available laboratory testing, including platelet function tests and genotyping for CYP2C19 variants.