Monitoring acetylsalicylic acid effects with the platelet function analyzer PFA-100.

The efficacy of acetylsalicylic acid (ASA) to prevent thrombotic or embolic events in patients with atherosclerosis was demonstrated in many large trials. Despite this fact, a subpopulation of patients experiences acute myocardial infarction or cerebrovascular ischemia indicating a nonresponsiveness to ASA. These patients would be candidates for an alternative or additional antiplatelet therapy, if they could be reliably identified. The aim of the monitoring of ASA therapy should be the identification of nonresponders to prevent a long-term intake of the drug without adequate benefit, to justify a dose escalation, or to initiate an alternative antiplatelet drug therapy. Considerable progress has been made in the measurement of platelet function. One of the novel devices employed is the platelet function analyzer PFA-100, which was already tested in several studies involving patients with atherothrombosis to detect nonresponsiveness to ASA. Many of these investigations indicate that the PFA-100 could be used for routine identification of nonresponders to ASA and--probably also--for tailoring antiplatelet therapy. The aim of this article is to summarize the data obtained from the studies focusing on the monitoring of ASA therapy by the PFA-100.