title: Reduced platelet activity is more common than reported anti-platelet medication use in patients with intracerebral hemorrhage.
abstract: BACKGROUND
  Anti-platelet medication and reduced platelet activity are associated with an increased risk of death after intracerebral hemorrhage (ICH). The optimal assay for assessing platelet activity is not defined. We hypothesized that reduced platelet activity would be common after ICH.
  
  
  METHODS
  We prospectively enrolled 72 consecutive patients with ICH and routinely measured platelet activity with both the PFA-100 (Siemens AG, Germany) and the VerifyNow-ASA (Accumetrics, CA, USA) systems on admission. We prospectively recorded anti-platelet medication use prior to ICH.
  
  
  RESULTS
  VerifyNow-ASA measurements were associated with aspirin (P = 0.001) and clopidogrel (P = 0.01) use prior to ICH. Combined clopidogrel and aspirin therapy was more potent than either alone. Of 33 patients with reduced platelet activity on the VerifyNow-ASA assay, 14 (42%) were not known to take anti-platelet agents. Of 27 patients with reduced platelet activity on the PFA-100, a related but different 14 (52%) were not known to take anti-platelet agents. There was a poor agreement between the assays (κ = 0.26, P = 0.07) on which patients had reduced platelet activity among the patients not known to take aspirin.
  
  
  CONCLUSIONS
  A medication history does not reliably identify patients with reduced platelet activity after ICH, and this may explain studies that found no association between known aspirin use and outcomes. Future studies should screen for unknown use of anti-platelet medications after ICH. Neither assay perfectly identified patients who reportedly used anti-platelet medication before ICH.
authors.affiliation: Department of Neurology, Northwestern University, 710 N Lake Shore Drive, Chicago, IL 60611, USA. a-naidech@northwestern.edu
authors.forename: Andrew M
authors.initials: AM
authors.lastname: Naidech
authors.forename: Sarice L
authors.initials: SL
authors.lastname: Bassin
authors.forename: Richard A
authors.initials: RA
authors.lastname: Bernstein
authors.forename: H Hunt
authors.initials: HH
authors.lastname: Batjer
authors.forename: Mark J
authors.initials: MJ
authors.lastname: Alberts
authors.forename: Paul F
authors.initials: PF
authors.lastname: Lindholm
authors.forename: Thomas P
authors.initials: TP
authors.lastname: Bleck
mesh_terms: D000368:Aged; D001241:Aspirin / Q000627:therapeutic use; D001792:Blood Platelets / Q000187:drug effects / Q000502:physiology; D002543:Cerebral Hemorrhage / Q000097:blood* / Q000188:drug therapy* / Q000453:epidemiology; D000077144:Clopidogrel; D004359:Drug Therapy, Combination; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D015539:Platelet Activation / Q000187:drug effects / Q000502:physiology*; D010975:Platelet Aggregation Inhibitors / Q000627:therapeutic use*; D010979:Platelet Function Tests; D011446:Prospective Studies; D012307:Risk Factors; D013988:Ticlopidine / Q000031:analogs & derivatives / Q000627:therapeutic use; D014859:Warfarin / Q000627:therapeutic use
chemical_list: D010975:Platelet Aggregation Inhibitors; D014859:Warfarin; D000077144:Clopidogrel; D013988:Ticlopidine; D001241:Aspirin