title: Comparison of Immature Platelet Count to Established Predictors of Platelet Reactivity During Thienopyridine Therapy.
abstract: Previous data suggest that reticulated platelets significantly affect antiplatelet response to thienopyridines. It is unknown whether parameters describing reticulated platelets can predict antiplatelet response to thienopyridines.
  
  
  
  The authors sought to determine the extent to which parameters describing reticulated platelets can predict antiplatelet response to thienopyridine loading compared with established predictors.
  
  
  
  This study randomized 300 patients undergoing elective coronary stenting to loading with clopidogrel 600 mg, prasugrel 30 mg, or prasugrel 60 mg. Adenosine diphosphate (ADP)-induced platelet reactivity was assessed by impedance aggregometry before loading (intrinsic platelet reactivity) and again on day 1 after loading. Multiple parameters of reticulated platelets were assessed by automated whole blood flow cytometry: absolute immature platelet count (IPC), immature platelet fraction, and highly fluorescent immature platelet fraction.
  
  
  
  Each parameter of reticulated platelets correlated significantly with ADP-induced platelet reactivity (p < 0.01 for all 3 parameters). In a multivariable model including all 3 parameters, only IPC remained a significant predictor of platelet reactivity (p < 0.001). In models adjusting each of the 3 parameters for known predictors of on-treatment platelet reactivity including cytochrome P450 2C19 (CYP2C19) polymorphisms, age, body mass index, diabetes, and intrinsic platelet reactivity, only IPC prevailed as an independent predictor (p = 0.001). In this model, IPC was the strongest predictor of on-treatment platelet reactivity followed by intrinsic platelet reactivity.
  
  
  
  IPC is the strongest independent platelet count-derived predictor of antiplatelet response to thienopyridine treatment. 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. (Impact of Extent of Clopidogrel-Induced Platelet Inhibition During Elective Stent Implantation on Clinical Event Rate-Advanced Loading Strategies [ExcelsiorLOAD]; DRKS00006102).
authors.affiliation: University Heart Center Freiburg Bad Krozingen, Department of Cardiology and Angiology II, Bad Krozingen, Germany. Electronic address: christian.stratz@universitaets-herzzentrum.de.
authors.forename: Christian
authors.initials: C
authors.lastname: Stratz
authors.affiliation: University Heart Center Freiburg Bad Krozingen, Department of Cardiology and Angiology II, Bad Krozingen, Germany.
authors.forename: Timo
authors.initials: T
authors.lastname: Bömicke
authors.affiliation: University Heart Center Freiburg Bad Krozingen, Department of Cardiology and Angiology II, Bad Krozingen, Germany.
authors.forename: Iris
authors.initials: I
authors.lastname: Younas
authors.affiliation: Institute of Experimental and Clinical Pharmacology and Toxicology, Friedrich-Alexander-Universitaet Erlangen-Nüernberg, Erlangen, Germany.
authors.forename: Anja
authors.initials: A
authors.lastname: Kittel
authors.affiliation: University Heart Center Freiburg Bad Krozingen, Department of Cardiology and Angiology II, Bad Krozingen, Germany.
authors.forename: Michael
authors.initials: M
authors.lastname: Amann
authors.affiliation: University Heart Center Freiburg Bad Krozingen, Department of Cardiology and Angiology II, Bad Krozingen, Germany.
authors.forename: Christian M
authors.initials: CM
authors.lastname: Valina
authors.affiliation: University Heart Center Freiburg Bad Krozingen, Department of Cardiology and Angiology II, Bad Krozingen, Germany.
authors.forename: Thomas
authors.initials: T
authors.lastname: Nührenberg
authors.affiliation: University Heart Center Freiburg Bad Krozingen, Department of Cardiology and Angiology II, Bad Krozingen, Germany.
authors.forename: Dietmar
authors.initials: D
authors.lastname: Trenk
authors.affiliation: University Heart Center Freiburg Bad Krozingen, Department of Cardiology and Angiology II, Bad Krozingen, Germany.
authors.forename: Franz-Josef
authors.initials: FJ
authors.lastname: Neumann
authors.affiliation: University Heart Center Freiburg Bad Krozingen, Department of Cardiology and Angiology II, Bad Krozingen, Germany.
authors.forename: Willibald
authors.initials: W
authors.lastname: Hochholzer
mesh_terms: D000368:Aged; D001792:Blood Platelets / Q000187:drug effects*; D003324:Coronary Artery Disease / Q000097:blood* / Q000188:drug therapy / Q000601:surgery; D004305:Dose-Response Relationship, Drug; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D062645:Percutaneous Coronary Intervention; D010974:Platelet Aggregation / Q000187:drug effects*; D010976:Platelet Count; D011725:Pyridines / Q000008:administration & dosage*; D015607:Stents; D016896:Treatment Outcome
chemical_list: D011725:Pyridines; C446540:thienopyridine
keywords: clopidogrel; percutaneous coronary intervention; prasugrel; reticulated platelets