title: Prevalence of platelet nonresponsiveness to aspirin in patients treated for secondary stroke prophylaxis and in patients with recurrent ischemic events.
abstract: To determine the prevalence of platelet nonresponsiveness to aspirin treatment for secondary stroke prophylaxis, the authors studied consecutive patients during a 29-month period. Information regarding their ischemic events, risk factors, and medications was collected. Platelet aggregation in response to collagen and arachidonic acid was used to determine platelet responsiveness to aspirin. A total of 653 patients were evaluated. Of these, 129 patients (20%) were determined to be nonresponsive to aspirin based on continued platelet aggregation in response to collagen, arachidonic acid, or both. A total of 87 (13%) of the 653 patients were clinical aspirin failures (ie, presented with new focal cerebral ischemic symptoms while taking aspirin). Of the patients with new cerebral ischemic symptoms, 57 (66%) were determined to be platelet nonresponsive to aspirin. The odds ratio for platelet nonresponsiveness to aspirin in patients who suffered a recurrent ischemic event while taking aspirin was 14.25 (95% confidence interval: 8.5-23.7; P < .5). Continued platelet aggregation despite aspirin treatment occurred in 20% of ambulatory patients treated for secondary stroke prophylaxis. The prevalence of nonresponsiveness to aspirin was statistically higher in those patients who suffered recurrent cerebral ischemia while taking aspirin (P < .5) compared with patients who remained without new ischemic symptoms.
authors.affiliation: Dent Neurologic Institute, 3980 Sheridan Drive, Amherst, NY 14226, USA. fgengo@buffalo.edu
authors.forename: Francis M
authors.initials: FM
authors.lastname: Gengo
authors.forename: Michelle
authors.initials: M
authors.lastname: Rainka
authors.forename: Matthew
authors.initials: M
authors.lastname: Robson
authors.forename: Michael F
authors.initials: MF
authors.lastname: Gengo
authors.forename: Alan
authors.initials: A
authors.lastname: Forrest
authors.forename: Maurice
authors.initials: M
authors.lastname: Hourihane
authors.forename: Vernice
authors.initials: V
authors.lastname: Bates
mesh_terms: D000367:Age Factors; D000368:Aged; D000893:Anti-Inflammatory Agents / Q000008:administration & dosage / Q000627:therapeutic use; D016718:Arachidonic Acid / Q000494:pharmacology; D001241:Aspirin / Q000008:administration & dosage / Q000627:therapeutic use*; D001792:Blood Platelets / Q000187:drug effects*; D000077144:Clopidogrel; D003094:Collagen / Q000494:pharmacology; D003324:Coronary Artery Disease / Q000150:complications; D004176:Dipyridamole / Q000008:administration & dosage / Q000627:therapeutic use; D004359:Drug Therapy, Combination; D005260:Female; D006801:Humans; D002546:Ischemic Attack, Transient / Q000097:blood / Q000517:prevention & control*; D008297:Male; D016017:Odds Ratio; D010974:Platelet Aggregation / Q000187:drug effects; D012008:Recurrence; D020521:Stroke / Q000097:blood / Q000209:etiology / Q000517:prevention & control*; D013988:Ticlopidine / Q000008:administration & dosage / Q000031:analogs & derivatives / Q000627:therapeutic use; D013997:Time Factors; D017211:Treatment Failure
chemical_list: D000893:Anti-Inflammatory Agents; D016718:Arachidonic Acid; D004176:Dipyridamole; D003094:Collagen; D000077144:Clopidogrel; D013988:Ticlopidine; D001241:Aspirin