Clopidogrel Platelet Function Tests

Platelet Function Testing Available at Mayo Clinic Florida

December 2011

In Mayo Clinic Florida, we have several tests available for platelet function testing. All evaluations of platelets should start with a CBC and peripheral blood smear to evaluate platelet number, morphology and granulation, as well as the morphology of the WBCs and RBCs. LTA is the gold standard and is frequently used to evaluate patients with congenital or acquired platelet abnormalities. The VerifyNow test is frequently utilized to detect resistance in patients who receive a loading dose of clopidogrel in preparation for neurosurgery such as a stent placement or for patients who have a thrombotic event while taking clopidogrel. PFA-100 is used in patients who are undergoing surgery and have a history of bleeding. Thromboelastography is used in liver transplant and other critical patients, but our institution does not currently do platelet mapping.

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Jump to section:

• Introduction
• Learning Objectives
• Platelet Function Tests for the Detection of Clopidogrel Resistance¹
• Platelet Function Tests for the Detection of Clopidogrel Resistance
• Caveat: There Is No Perfect Platelet Function Test...
• Problems With Testing For Clopidogrel
• How We Choose a Testing Method
• Methodology Table
• Platelet Function Testing Available at Mayo Clinic Florida
• Light Transmission Platelet Aggregometry Studies (LTA)
• Platelet Aggregation (Cont'd)
• Normal Patient
• Accumetrics VerifyNow Test
• VerifyNow P2Y₁₂ Test
• P2Y₁₂ Test Interferences
• P2Y₁₂ Antagonists²
• Can These Platelet Function Tests Be Used for Ticagrelor (Brilinta/Brilique)?
• PFA-100
• PFA–100 (Cont'd)
• INNOVANCE PFA P2Y
• TEG — Platelet Mapping
• Results of VerifyNow Testing
• 2009–2011 Clopidogrel Response at 30%
• Genetic Testing: Clopidogrel Metabolism
• Clopidogrel Metabolism
• Number of Gene Polymorphisms
• Clopidogrel Metabolism and Genetic Polymorphisms
• Why Do Genetic Testing?
• Clopidogrel Genetics (Cont'd)
• Caveats — Other Reasons for Poor Response to Clopidogrel
• CYP2C19 Polymorphism May Require Another Factor
• Controversy for Clopidogrel
• Warning: Diminished Effectiveness In Poor Metabolizers
• What Does Warning Mean For Clinicians With Patients On Clopidogrel?
• FDA Answer
• More Questions
• Summary
• References
• Questions?
• Disclosure