Summary
The essential role of platelets in haemostasis underlies the relationship between
platelet function and spontaneous or procedure-related bleeding, which has important
prognostic implications. Although not routinely undertaken, platelet function testing
offers the potential to tailor antiplatelet therapy for individual patients. However,
uncertainties remain about how well platelet function testing may predict haemostasis
and guide management of bleeding risk. Studies of aspirin, P2Y12 inhibitors and other antiplatelet drugs clearly demonstrate how inhibition of platelet
function increases bleeding risk. More potent antiplatelet drugs are associated with
higher bleeding rates, consistent with the levels of platelet inhibition achieved
by these drugs. Studies of patients treated with clopidogrel, which is associated
with wide inter-individual variation in antiplatelet effect, suggest that platelet
function testing may predict bleeding risk related to coronary artery bypass grafting
(CABG) surgery and potentially guide the timing of surgery following discontinuation
of clopidogrel. Similarly, some studies have demonstrated a relationship between clopidogrel
response and bleeding in patients undergoing percutaneous coronary intervention (PCI),
although other studies have not supported this. Carriage of the *17 allele of cytochrome
P450 2C19, which is associated with gain of function and enhanced response to clopidogrel,
seems to be associated with increased bleeding risk, although studies showing lack
of apparent effect of loss-of-function alleles provide contradictory evidence. Further
large studies are needed to guide best practice in the application of platelet function
testing in the clinical management of patients treated with antiplatelet drugs in
order to optimise individual care.
Keywords
ADP receptors - antiplatelet agents - clinical trials - antiplatelet drugs - haemostasis
- platelet pharmacology
