A New Clopidogrel (Plavix) Point-of-Care Assay: Rapid Determination of Antiplatelet Activity in Trauma Patients

INTRODUCTION: An increasing proportion of trauma patients are on anticoagulation or antiplatelet therapy. Unlike warfarin, where measuring international normalized ratio can help direct management, measuring platelet inhibition from clopidogrel (Plavix) is not standardized. We report the use of a new P2Y12 point-of-care assay (VerifyNow; Accumetrics, San Diego, CA) to determine the magnitude of platelet inhibition in trauma patients using clopidogrel. METHODS: Trauma patients in 2009 were queried for clopidogrel use by prehospital personnel and the trauma team. Blood was obtained on admission for patients reportedly taking clopidogrel and was assayed for platelet inhibition using the VerfiyNow-P2Y12 device that measures P2Y12 reaction units and photometrically determines platelet inhibition percentage within 30 minutes. Patient demographics including age, Injury Severity Score, mechanism of injury, and complications from hemorrhage were also analyzed. RESULTS: In the time studied, 46 patients taking clopidogrel were assayed for platelet inhibition. The mean age was 75.9 years±11.8 years, and the most common mechanism of injury was fall (86.9%). Platelet inhibition ranged from 0% to 89%. There were no deaths, and only two patients, from the 0% and>30% inhibition group, had hemorrhagic complications (increased intracranial hemorrhage). CONCLUSIONS: The P2Y12 point-of-care assay determined that a large percentage of patients had undetectable or low platelet inhibition despite reportedly being on clopidogrel therapy. These patients may be clopidogrel nonresponders or noncompliant. It is unlikely that clopidogrel reversal therapies, such as platelet transfusions or Desmopressin, would be beneficial in this group. Further studies stratifying the percent platelet inhibition needed to increase bleeding complications is warranted to optimize management strategies.