Prevalences widely differ between studies reporting on aspirin resistance .
BACKGROUND The absolute risk of recurrences among patients using aspirin for prevention of cardiovascular events remains high .
Persistent platelet reactivity despite aspirin therapy might explain this in part .
Reported prevalences of this so-called aspirin resistance vary widely , between 0 % and 57 % .
OBJECTIVES The aim of the study was to systematic ally review all available evidence on prevalence of aspirin resistance and to study determinants of reported prevalence .
In vitro aspirin resistance detected by PFA‐100TM closure time: pivotal role of plasma von Willebrand factor
The in vitro closure time ( CT ) , determined by the Platelet Function Analyzer ( PFA‐100TM ) , is used to monitor patients treated with aspirin . A relatively high percentage of in vitro aspirin resistance was reported despite an adequate inhibition of platelet response to arachidonic acid and we investigated whether high plasma levels of von Willebr and factor ristocetin cofactor activity ( vWF : RCo ) may contribute to this profile . Platelet aggregation test , CT [ collagen adrenaline ( CEPI‐CT ) and collagen adenosine 5′‐diphosphate ( ADP ) ( CADP‐CT ) ] , and vWF : RCo levels were evaluated in 55 consecutive patients receiving aspirin ( 75–250 mg/d ) versus 32 untreated control subjects . All the aspirin‐treated patients showed platelet aggregation responses that reflected the aspirin intake . However , CT data analysis enabled aspirin good‐responder ( GR ) and aspirin bad‐responder ( BR ) patients to be identified . All GR group subjects ( n = 27 ) , had a CEPI‐CT and a CADP‐CT longer than 300 s and 96 s respectively . The BR group ( n = 28 ) had CEPI‐CT values below 200 s and all CADP‐CT were in the normal range ( 77 ± 19 s ) . Interestingly , the BR plasma vWF : RCo levels were significantly higher ( 159 ± 43 % ) than those of the GR group ( 121 ± 34 % ) ( P < 0·01 ) , which were similar to control values ( 114 ± 31 % ) . A negative correlation between vWF : RCo and CT values was established . We demonstrate that in vitro  aspirin‐resistance , revealed by PFA‐100TM CT prolongation failure , is correlated to increased plasmatic vWF : RCo levels , reinforcing its particular importance in PFA‐100TM cartridges performance
Prevalences widely differ between studies reporting on aspirin resistance .
BACKGROUND The absolute risk of recurrences among patients using aspirin for prevention of cardiovascular events remains high .
Persistent platelet reactivity despite aspirin therapy might explain this in part .
Reported prevalences of this so-called aspirin resistance vary widely , between 0 % and 57 % .
OBJECTIVES The aim of the study was to systematic ally review all available evidence on prevalence of aspirin resistance and to study determinants of reported prevalence .