CYP2C19 (Plavix test)

The CYP2C19 test identifies individuals who are slow metabolizers of clopidogrel, meaning they would require a higher dose of clopidogrel (or a different anticoagulant) in order to decrease the risk of a blood clot and stent closure. 1 Patients can have one or two gene mutations (alleles). “One reduced function allele incurs a 55% increased risk of CV death, MI, ischemic stroke and 2.5-fold increased risk of stent occlusion.  Two reduced function alleles have a 76% increased risk of cardiovascular death, heart attack, or ischemic stroke and a 4-fold increase risk of stent occlusion.”

The CYP2C19 test also identifies patients who are rapid metabolizers of clopidogrel. These patients necessitate a lower dose of clopidogrel (or a different anticoagulant) in order to prevent bleeding complications.

We now have other anti-coagulant options available, so there is no reason to prescribe clopidogrel unless the patient is a normal metabolizer. Prasurgrel (Effient) and ticagrelor (Brilinta) are alternative P2Y12 inhibitors, which do not depend on CYP2C19. In studies, these medications were shown to be superior to clopidogrel in preventing cardiovascular events in patients with acute coronary syndrome (ACS), but they are more expensive and have been associated with an increased bleeding risk. 2 These pharmaceutical companies could tout superiority because the patient’s genetics were not assessed during the trials. In a study of nearly 2,000 patients on Plavix, the risk for heart attack, stroke, and death was significantly higher in patients with the CYP2C19 genotype, but in patients who were normal CYP2C19 metabolizers, there was no difference seen in event rates between patients on Plavix versus another anticoagulant. 2

I have spoken to cardiologists who say they just wait until a patient has a second event (a clot or a bleed) to change the patient’s blood thinner. Sadly, some patients will not survive their second event. We have the tools available now to assist our decision-making regarding these potential life-saving treatments so our patients can attain better outcomes.

The potential benefits of genotype-guided anti-platelet therapy are clear, despite current guidelines failing to recommend it. 2 This test is an absolute necessity for any patient currently taking (or considering taking) clopidogrel.