The assessment of platelet function

SUMMARY Platelet activation is involved in physiological hemostasis and in a variety of thromboembolic events leading to stroke, myocardial ischemia, and other organ dysfunction. Apart from congenital platelet dysfunction, acquired platelet defects are increasingly common in patients due to the widespread use of antiplatelet agents. Newer antiplatelet agents targeting platelet glycoprotein IIb–IIIa and adenosine‐5′‐diphosphate receptors inhibit platelet activation, and therefore assessing platelet inhibition may be important to prevent major bleeding, especially before a surgical intervention. In the past decade, the knowledge from genotypic analyses and prospective outcome studies suggested inter‐patient variability in the therapeutic response to antiplatelet therapies, which further stresses the need for individual platelet testing. In managing bleeding patients, platelet transfusion may be better guided by the use of platelet function tests because transfusion therapy is costly and potentially harmful if administered inappropriately. Basic understanding of the hemostatic roles of platelets, etiologies of platelet defects, and characteristics of current platelet assessment methods should help physicians who manage complex coagulation issues in critically ill patients.