Test Code: 904468


Clinical Use

  • Enables early identification of cardiovascular patients who are predisposed to poor Clopidogrel bisulfate response and therefore at risk for recurrent cardiovascular events
  • May help guide treatment strategy for patients being considered for or receiving Clopidogrel bisulfate therapy
  • Convenient sampling includes 2 options:
    o Whole blood
    o Saliva (non-invasive); Specimen can be collected at home prior to procedure

Clinical Background

Clopidogrel (Plavix®’) bisulfate is widely used to treat patients who have had a previous cardiovascular event and to prevent stent thrombosis following stent implantation. This antiplatelet drug, however, is less effective in the 30% of Caucasians, 40% of Africans, and >55% of East Asians who have a reduced-function mutation in the CYP2C19 gene.1,2 This gene encodes the cytochrome P450 2C19 enzyme that metabolizes Clopidogrel bisulfate to its active form.

Patients with two CYP2C19*1 (wild type) alleles metabolize Clopidogrel bisulfate efficiently (extensive metabolizers) and respond normally to Clopidogrel bisulfate therapy. However, patients with one or more mutated CYP2C19 alleles such as CYP2C19*2, *3, *4, or *5 do not metabolize Clopidogrel bisulfate as well. These patients have either one mutated allele and one wild-type allele (intermediate metabolizers) or two mutated alleles (poor metabolizers). Intermediate and poor metabolizers have a reduced response to Clopidogrel bisulfate and are at higher risk of recurrent cardiovascular events and stent thrombosis.3-5

The laboratory-developed AccuType™ CP test can be used to identify intermediate and poor metabolizers who are likely to respond poorly to Clopidogrel bisulfate. These patients may be considered for a higher Clopidogrel bisulfate dose or treated with a different antiplatelet therapy such as Prasugrel, which does not require activation by CYP2C19.6,7 Testing saliva specimens that are collected at home prior to stent implantation may allow clinicians to obtain test results and, if needed, adjust antiplatelet treatment strategy before the procedure.

Besides Clopidogrel bisulfate metabolism, other factors including Clopidogrel bisulfate absorption, concomitant medications (eg, Omeprazole), obesity, insulin resistance, and inadequate compliance impact an individual’s response to Clopidogrel bisulfate.5,8


Specimen Requirements

  • 4.0 mL of room temperature whole blood from an EDTA lavender-top tube (2.0 mL minimum). Alternately, submit 1.0 mL room temperature saliva collected in Oragene DNA self-collection kit.

CPT Codes*

83891; 83892 (x2); 83900; 83901 (x2); 83909; 83914 (x4); 83912


Method

Polymerase Chain Reaction (PCR); Single Nucleotide Primer Extension (SNPE)


References

  1. Myrand SP, Sekiguchi K, Man MZ, et al. Pharmacokinetics/genotype associations for major cytochrome P450 enzymes in native and first- and third-generation Japanese populations: comparison with Korean, Chinese, and Caucasian populations. Clin Pharmacol Ther. 2008;84:347-361.
  2. Dandara C, Masimirembwa CM, Magimba A, et al. Genetic polymorphism of CYP2D6 and CYP2C19 in east- and southern African populations including psychiatric patients. Eur J Clin Pharmacol. 2001;57:11-17.
  3. Mega JL, Close SL, Wiviott SD, et al. Cytochrome P-450 polymorphisms and response to clopidogrel. N Engl J Med. 2009;360:354-362.
  4. Shuldiner AR, O’Connell JR, Bliden KP, et al. Association of cytochrome P450 2C19 genotype with the antiplatelet effect and clinical efficacy of clopidogrel therapy. JAMA. 2009;302:849-857.
  5. Simon T, Verstuyft C, Mary-Krause M, et al. Genetic determinants of response to clopidogrel and cardiovascular events. N Engl J Med. 2009;360:363-375.
  6. Mega JL, Close SL, Wiviott SD, et al. Cytochrome P450 genetic polymorphisms and the response to prasugrel: relationship to pharmacokinetic, pharmacodynamic, and clinical outcomes. Circulation. 2009;119:2553-2560.
  7. Brandt JT, Close SL, Iturria SJ, et al. Common polymorphisms of CYP2C19 and CYP2C9 affect the pharmacokinetic and pharmacodynamic response to clopidogrel but not prasugrel. J Thromb Haemost. 2007;5:2429-2436.
  8. Toth PP, Armani A. Thienopyridine therapy and risk for cardiovascular events in secondary prevention. Curr Atheroscler Rep. 2009;11:364-370.

*The CPT codes provided are based on AMA guidelines and are for informational purposes only. CPT coding is the sole responsibility of the billing party. Please direct any questions regarding coding to the payor being billed.

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