title: Clopidogrel-induced platelet inhibition cannot be detected by the platelet function analyzer-100 system in stroke patients.
abstract: The administration of an adenosine diphosphate (ADP) receptor antagonist, such as clopidogrel, is recommended for recurrent stroke patients under aspirin treatment. However, up to 25% of vascular patients have an inadequate response to clopidogrel treatment, which could be associated with increased reinfarction rates. This study investigated whether the platelet function analyzer (PFA-100) system represents an appropriate tool for monitoring clopidogrel's antiplatelet effects in stroke patients. Sixteen stroke patients on clopidogrel therapy (75 mg/day) were included in a prospective analyst-blinded, cross-sectional study. Platelet function was assayed by collagen/epinephrine (CEPI)- and collagen/ADP (CADP)-induced closure times (CTs) using the PFA-100 system. von Willebrand factor antigen (vWF-Ag) levels were measured by enzyme immunoassay. CEPI-CT and CADP-CT values averaged 160 +/- 15 seconds and 102 +/- 10 seconds, respectively, and were in the normal range. vWF-Ag concentrations averaged 153 +/- 17% and correlated inversely with CTs (r = .71; P < .002 for CEPI-CT, r = .54; P < .04 for CADP-CT). Our data indicate that the current PFA-100 cartridges are not sufficiently sensitive to detect clopidogrel-induced platelet inhibition in stroke patients.
authors.affiliation: Department of Neurology, Medical University Vienna, Austria. nicole.kotzailias@meduniwien.ac.at
authors.forename: Nicole
authors.initials: N
authors.lastname: Kotzailias
authors.forename: Kirsten
authors.initials: K
authors.lastname: Elwischger
authors.forename: Thomas
authors.initials: T
authors.lastname: Sycha
authors.forename: Walter
authors.initials: W
authors.lastname: Rinner
authors.forename: Peter
authors.initials: P
authors.lastname: Quehenberger
authors.forename: Eduard
authors.initials: E
authors.lastname: Auff
authors.forename: Christian
authors.initials: C
authors.lastname: Müller
mesh_terms: D000244:Adenosine Diphosphate; D000368:Aged; D001760:Bleeding Time / Q000295:instrumentation*; D000077144:Clopidogrel; D003094:Collagen; D003430:Cross-Sectional Studies; D016903:Drug Monitoring / Q000295:instrumentation* / Q000379:methods; D004351:Drug Resistance; D004837:Epinephrine; D005260:Female; D006400:Hematocrit; D006801:Humans; D008297:Male; D008875:Middle Aged; D010974:Platelet Aggregation / Q000187:drug effects*; D010975:Platelet Aggregation Inhibitors / Q000494:pharmacology / Q000627:therapeutic use*; D011446:Prospective Studies; D015203:Reproducibility of Results; D055502:Secondary Prevention; D020521:Stroke / Q000097:blood / Q000188:drug therapy*; D013988:Ticlopidine / Q000031:analogs & derivatives* / Q000494:pharmacology / Q000627:therapeutic use; D013997:Time Factors; D014841:von Willebrand Factor / Q000378:metabolism
chemical_list: D010975:Platelet Aggregation Inhibitors; D014841:von Willebrand Factor; D000244:Adenosine Diphosphate; D003094:Collagen; D000077144:Clopidogrel; D013988:Ticlopidine; D004837:Epinephrine