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01-04-2012 | Cardiology | Article

Genetic test effectively protects patients with clopidogrel sensitivity


Free abstract

MedWire News: Point-of-care genetic testing for the CYP2C19*2 allele effectively identifies and protects patients undergoing percutaneous coronary intervention (PCI) from having major adverse events as a result of clopidogrel treatment.

The researchers showed that all the patients who underwent point-of-care testing with the Spartan RX CYP2C19 (Spartan Biosciences, Ottawa, Ontario, Canada) test who had the CYP2C19*2 allele were identified and given prasugrel as an alternative anticoagulant therapy. By contrast, 30% of patients with the variant in the standard care group were given clopidogrel instead of prasugrel putting them at high risk for adverse events.

As reported in The Lancet, Derek So (University of Ottawa Heart Institute, Canada) and colleagues enrolled 200 patients due to undergo PCI for acute coronary syndrome or stable angina to take part in a study to assess the efficacy of the Spartan RX CYP2C19 point-of-care test. The test is easy to use and involves taking a buccal swab from the patient's mouth.

The participants were assigned to receive rapid CYP2C19*2 genotyping, following which carriers were prescribed prasugrel 10 mg/day and noncarriers clopidogrel 75 mg/day; or standard care, which involved all patients being prescribed clopidogrel 75 mg/day.

The patients were followed up at 7 days, at which point a P2Y12 reactivity unit value of more than 234 (indicating high platelet reactivity) was considered to indicate a high risk for major adverse events.

In total, 187 patients completed follow up at 7 days. Of these, 91 had undergone rapid genotyping and 96 had been prescribed standard treatment.

All 23 CYP2C19*2 allele carriers were picked up by the Spartan RX CYP2C19 test and were prescribed prasugrel. None had high platelet reactivity at 7 days.

In the standard care group, genetic testing (via conventional laboratory methods) did not occur until day 7, at which point 23 patients were identified as having at least one copy of CYP2C19*2, all of whom had been treated with clopidogrel. Of these patients, seven (30%) had high platelet reactivity.

"For the first time in medicine, nurses were able to perform DNA testing at the patient's bedside. This is a significant step towards the vision of personalized medicine," said So.

The researchers concede that use of platelet reactivity as a surrogate endpoint was not ideal, but say: "Our findings suggest that personalisation of antiplatelet therapy might reduce adverse ischaemic outcomes," adding that the "use of prasugrel only in high-risk individuals might also minimise adverse bleeding events."

They conclude: "The development of practical point-of-care genetic testing in our study will help to integrate genetics into the clinical setting and will allow large-scale investigations to definitively assess the value of pharmacogenetic strategies."

By Helen Albert

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