title: Aspirin non-responder status in patients with recurrent cerebral ischemic attacks.
abstract: BACKGROUND
  Antiplatelet agents such as acetylsalicylic acid (aspirin) reduce the relative risk for cerebrovascular events in patients with cardiovascular or cerebrovascular disorders by approximately 23 %. Recent observations raise the possibility that aspirin resistance may contribute to the failure of aspirin treatment in a significant proportion of patients (aspirin non-responders). To evaluate the clinical relevance of aspirin non-responder status, we analysed platelet functions in symptomatic and asymptomatic patients treated with aspirin for secondary prevention of cardiovascular and cerebrovascular events.
  
  
  METHODS
  A total of 53 patients on 100 mg aspirin daily for secondary prevention (mean treatment duration > 60 months) were included. Patients were categorized as asymptomatic if they were free of cerebrovascular incidents for at least 24 months (n = 18). Symptomatic patients had suffered ischemic strokes or transient ischemic attacks within the previous 3 days (n = 35). Platelet function was assessed using the PFA-100 system that allows for quantitative assessment of platelet function, reporting platelet aggregatability as the time required to close a small aperture in a biologically active membrane.
  
  
  RESULTS
  Collagen/epinephrine closure times were significantly shorter in symptomatic patients than in asymptomatic patients (p < 0.01). Individual closing times were normal in 12 of 35 symptomatic patients (34 % non-responders) whereas all asymptomatic patients had prolonged closure times.
  
  
  CONCLUSIONS
  Aspirin non-responder status may contribute to failure of aspirin therapy in the secondary prevention of cerebrovascular incidents in as much as 30-40 % of patients. Quantitative assessment of platelet functions may provide a means to predict aspirin treatment failure in individual patients and to re-direct therapeutic strategies.
authors.affiliation: Department of Neurology, University of Tübingen, Tübingen, Germany.
authors.forename: K
authors.initials: K
authors.lastname: Grundmann
authors.forename: K
authors.initials: K
authors.lastname: Jaschonek
authors.forename: B
authors.initials: B
authors.lastname: Kleine
authors.forename: J
authors.initials: J
authors.lastname: Dichgans
authors.forename: H
authors.initials: H
authors.lastname: Topka
mesh_terms: D000368:Aged; D001241:Aspirin / Q000494:pharmacology / Q000627:therapeutic use*; D005260:Female; D006801:Humans; D002546:Ischemic Attack, Transient / Q000188:drug therapy* / Q000517:prevention & control*; D008297:Male; D008875:Middle Aged; D010974:Platelet Aggregation / Q000187:drug effects*; D010975:Platelet Aggregation Inhibitors / Q000627:therapeutic use*; D010979:Platelet Function Tests; D055502:Secondary Prevention
chemical_list: D010975:Platelet Aggregation Inhibitors; D001241:Aspirin