A novel fifteen minute test for assessment of individual time-dependent clotting responses to aspirin and clopidogrel using modified thrombelastography

Background: A rapid, reliable, point of care test reflecting patient specific responses to antiplatelet therapy would be of great clinical value in percutaneous coronary intervention (PCI). The aim of this study was to establish whether modified thrombelastography (TEG) can be employed as a 15 minute test of individual patient responses to aspirin and clopidogrel using a novel parameter, percentage clotting inhibition (% CIn). Methods and results: Thirty healthy volunteers and 10 patients undergoing elective PCI were recruited into four groups: 10 volunteers received a single 300mg dose of aspirin [A1]: 10 volunteers received aspirin 75mg daily for 7 days [A2]: 10 volunteers received a 600 mg dose of clopidogrel [C1]: 10 patients received a 600mg loading dose of clopidogrel prior to elective PCI [C2]. In all cases the area under the clotting response curve was measured at 15 minutes (AUC15) and used to calculate a novel parameter, percentage clotting inhibition (% CIn). Large differences were demonstrated in both aspirin and clopidogrel groups in response to therapy as assessed by both the area under the curve at 15 minutes and % CIn. Furthermore, the technique demonstrated important heterogeneity of time-dependent responses between individuals. Conclusion: Modified TEG, employing AUC15 and % CIn, is a promising tool for assessing responses to aspirin and clopidogrel. Further data are now required to assess the potential of this test to optimise individual therapy in PCI patients in order to detect and treat those patients with relative hypo-responsiveness to anti-platelet drugs.