The Use of Platelet Function Assays May Help to Determine Appropriate Antiplatelet Treatment Options in a Patient With Recurrent Stroke on Baby Aspirin

Patients with ischemic stroke of arterial origin are commonly prescribed aspirin because it has been shown in placebo-controlled trials to reduce the risk of a recurrent stroke and other major vascular events by approximately 13% (95% CI, 6% to 19%).1,2 The mechanism by which aspirin “works” is that, at doses as low as 0.5 mg/kg, it irreversibly inactivates platelet cyclo-oxygenase-1 by at least 95% and thereby blocks the generation of thromboxane, a platelet agonist and potent vasoconstrictor.2If patients experience a recurrent arterial ischemic stroke at the time of taking low-dose (50 to 100 mg per day) “baby” aspirin, it is reasonable to ask whether the recurrence was due to a “failure” of low-dose aspirin to fully inhibit platelet cyclo-oxygenase-1 (and platelet function).3 In the same way that we measure the international normalized ratio to monitor and adjust warfarin therapy, it is reasonable to question whether platelet function assays could help determine future antiplatelet treatment options in patients with recurrent arterial ischemic stroke at the time of taking baby aspirin.A variety of laboratory assays of the antiplatelet effects of aspirin are …