Absolute immature platelet count predicts thienopyridine response
medwireNews: An elevated absolute immature platelet count (IPC) is a significant indicator of reduced inhibition of platelet aggregation in response to thienopyridine loading in stable patients undergoing percutaneous coronary intervention, German researchers report.
Furthermore, the association of IPC with on-treatment platelet reactivity varied according to the loading regimen used and weakened with higher antiplatelet potency.
This finding is “important” and “may have clinical impact in settings associated with high IPC, such as acute coronary syndrome”, say Christian Stratz (University Heart Center Freiburg Bad Krozingen) and co-authors of the study.
The researchers investigated whether parameters of reticulated platelets could predict platelet reactivity in 300 patients undergoing elective coronary stenting randomly assigned to undergo loading with clopidogrel 600 mg, prasugrel 30 mg or prasugrel 60 mg.
As reported in the Journal of the American College of Cardiology, IPC, immature platelet fraction and highly fluorescent immature platelet fraction – assessed by automated whole blood flow cytometry – all significantly and positively correlated with adenosine diphosphate-induced platelet reactivity, as measured by impedance aggregometry.
However, only IPC was independently associated with on-treatment platelet reactivity in a multivariable analysis adjusted for known predictors of antiplatelet response to thienopyridines such as cytochrome P450 2C19 (CYP2C19) polymorphisms, age, body mass index, diabetes and intrinsic platelet reactivity.
In this model, 4% of the observed variability in platelet reactivity was attributed to IPC.
Stratz and team also found that there was a significant interaction between the allocated treatment regimen and the effect of IPC on on-treatment platelet reactivity.
Specifically, the strongest effect was observed in the clopidogrel 600 mg group, for whom 7% of on-clopidogrel platelet reactivity could be explained by IPC. This compared with 5% of on-prasugrel 30 mg platelet reactivity and no significant interaction for prasugrel 60 mg.
The researchers conclude: “Given its easy availability, together with its even stronger association with on-treatment platelet reactivity compared with known predictors, including the CYP2C19*2 polymorphism, IPC may become the preferred predictor of antiplatelet response to thienopyridine treatment.”
By Laura Cowen
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