How do you order a genetic clopidogrel (Plavix) study?

From the Guidelines

To order a genetic clopidogrel (Plavix) study, request a CYP2C19 genotype test through your hospital's electronic medical record system or by completing a laboratory requisition form, as this is crucial in identifying patients who may not respond adequately to clopidogrel due to genetic variations, as recommended by the American College of Medical Genetics and Genomics 1. When ordering the test, specify that it is to assess clopidogrel metabolism status. The test typically requires a blood sample (3-5 mL in an EDTA tube) or sometimes a buccal swab. It is essential to include relevant clinical information such as the patient's current or planned antiplatelet therapy and any history of cardiovascular events or stent placement. The results of the CYP2C19 genotype test will categorize the patient as a normal, intermediate, poor, or ultrarapid metabolizer of clopidogrel. This genetic testing is important because approximately 30% of patients carry CYP2C19 variants that reduce their ability to convert clopidogrel to its active form, potentially leading to treatment failure and increased risk of adverse cardiovascular events, as highlighted in the technical standard of the American College of Medical Genetics and Genomics 1. For patients identified as poor metabolizers, alternative antiplatelet agents such as ticagrelor (Brilinta) or prasugrel (Effient) may be more appropriate as they are not significantly affected by CYP2C19 genetic variations, according to the meta-analysis of 7 randomized controlled trials 1. Key points to consider when ordering a genetic clopidogrel study include:

• The patient's risk for poor clinical outcomes and potential for inadequate platelet inhibition with clopidogrel
• The possibility of using alternative P2Y12 inhibitors like prasugrel or ticagrelor for patients with identified genetic predispositions to poor clopidogrel response, as suggested in guidelines from the American College of Cardiology Foundation/American Heart Association Task Force on Practice Guidelines and the Society for Cardiovascular Angiography and Interventions 1.

From the FDA Drug Label

Your doctor may do genetic tests to make sure clopidogrel tablets are right for you.

To order a genetic clopidogrel (Plavix) study, you should consult with your doctor. They will determine if a genetic test is necessary to ensure that clopidogrel is suitable for you. The test will help identify if you have certain genetic factors that may affect how your body breaks down clopidogrel. Your doctor will then use this information to decide on the best course of treatment for you 2.

From the Research

Ordering a Genetic Clopidogrel (Plavix) Study

To order a genetic clopidogrel (Plavix) study, the following steps can be considered:

• Identify the need for CYP2C19 genotyping to guide antiplatelet therapy selection, particularly in patients undergoing percutaneous coronary intervention (PCI) or at risk of adverse cardiovascular and cerebrovascular events 3.
• Choose a validated CYP2C19 genotyping assay, such as the Spartan RX CYP2C19 System, which can utilize blood samples 4.
• Ensure that the selected assay can detect relevant CYP2C19 alleles, including *1, *2, *3, and *17, to identify poor metabolizers and guide therapy selection 5.
• Consider the clinical utility of CYP2C19 genotype-guided antiplatelet therapy, including the potential to reduce major adverse cardiovascular events (MACEs) and improve patient outcomes 6, 3.

Available Assays and Testing Methods

Some available assays and testing methods for CYP2C19 genotyping include:

• TaqMan real-time polymerase chain reaction primers and probes 5
• Spartan RX CYP2C19 System, which can utilize blood samples or buccal swabs 4
• Other validated CYP2C19 genotyping assays that can detect relevant alleles and guide therapy selection

Clinical Implications and Considerations

When ordering a genetic clopidogrel study, consider the following:

• The potential impact of CYP2C19 genotype on clopidogrel response and patient outcomes 7, 6, 3
• The clinical utility of CYP2C19 genotype-guided antiplatelet therapy in reducing MACEs and improving patient outcomes 6, 3
• The need for careful interpretation of genotyping results and consideration of other factors that may influence patient response to clopidogrel 7, 3