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 .
Screening for Aspirin Responsiveness After Transient Ischemic Attack and Stroke: Comparison of 2 Point-of-Care Platelet Function Tests With Optical Aggregometry
Background and Purpose — Recent studies suggest that patients who do not respond to aspirin ( ASA ) therapy may be at increased risk of ischemic vascular events . The availability of simple to use point-of-care ( POC ) platelet function tests now potentially allows aspirin nonresponsiveness to be identified in routine clinical practice . However , there are very few data on whether the different tests produce consistent results . We therefore compared 2 POC tests ( PFA-100 device and the Ultegra-RPFA [ RPFA ] ) with conventional light transmission aggregometry ( LTA ) . Methods — Platelet function was assessed by all 3 tests in 100 patients receiving low-dose ASA therapy after transient ischemic attack ( TIA ) or ischemic stroke . Results — The incidence of ASA nonresponsiveness was 17 % by the RPFA and 22 % by the PFA-100 , compared with only 5 % by LTA ( ie , as defined with both arachidonic acid and ADP ) . Agreement between the RPFA and the PFA-100 and arachidonic acid induced LTA was poor ( & kgr;=0.16 , 95 % CI , −0.08 to 0.39 , P=0.11 ; and & kgr;=0.09 −0.12 to 0.30 , P=0.32 , respectively ) . Agreement between the 2 POC tests was also poor ( & kgr;=0.14 , −0.08 to 0.36 , P=0.15 ) . Only 2 % of patients were aspirin nonresponders by all 3 tests . Conclusions — The prevalence of apparent ASA nonresponsiveness was higher with both the POC tests than with LTA . However , agreement between the tests was poor and very few patients were ASA nonresponsive by all 3 tests . Aspirin nonresponsiveness is therefore highly test-specific and large prospect i ve studies will be required to determine the prognostic value of each of the separate tests
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 .