title: Incomplete inhibition of platelet function as assessed by the platelet function analyzer (PFA-100) identifies a subset of cardiovascular patients with high residual platelet response while on aspirin.
abstract: Sixty-six patients with a history of ischemic events (myocardial infarction, unstable angina, or stroke) on chronic aspirin therapy were studied by different platelet function tests: 37 patients had suffered a recurrent event while on aspirin and 29 were without recurrences. Based on results from light transmission aggregometry (LTA) induced by arachidonic acid (AA) and serum TxB(2) both COX-1-dependent methods, only one patient could be identified as aspirin "resistant". However, when methods only partially-dependent on platelet COX-1 activity were considered, the prevalence of aspirin non-responders ranged, according to the different tests, from 0 to 52%. No difference was observed between patients with recurrences and those without. Among patients with recurrent events, those with an incomplete inhibition of platelet function, as assessed by the PFA-100, had significantly higher residual serum TxB(2) (2.4 ± 2.4 ng/mL vs 0.4 ± 0.1 ng/mL, p = 0.03), residual LTA-AA (9.2 ± 10.6% vs 2.0 ± 1.6%, p = 0.008), LTA-Coll (49.3 ± 14.6% vs 10.2 ± 8.3%, p = 0.007) and LTA-ADP (50.9 ± 16.2% vs 34.3 ± 11.0%, p = 0.04). In conclusion, laboratory tests solely exploring the AA-mediated pathway of platelet function, while being the most appropriate to detect the effect of aspirin on its pharmacologic target (platelet COX-1), may fail to reveal the functional interactions between minimal residual TxA(2) and additional stimuli or primers potentially leading to aspirin-insensitive platelet aggregation. High residual platelet response in platelet function tests only partially dependent on COX-1 may reveal a condition of persistent platelet reactivity in a subset of aspirin-treated patients characterizing them as a subgroup at higher vascular risk.
authors.affiliation: Department of Internal Medicine, University of Perugia, Italy.
authors.forename: M
authors.initials: M
authors.lastname: Crescente
authors.forename: A M
authors.initials: AM
authors.lastname: Mezzasoma
authors.forename: M
authors.initials: M
authors.lastname: Del Pinto
authors.forename: F
authors.initials: F
authors.lastname: Palmerini
authors.forename: A
authors.initials: A
authors.lastname: Di Castelnuovo
authors.forename: C
authors.initials: C
authors.lastname: Cerletti
authors.forename: G
authors.initials: G
authors.lastname: De Gaetano
authors.forename: P
authors.initials: P
authors.lastname: Gresele
mesh_terms: D000368:Aged; D001241:Aspirin / Q000008:administration & dosage*; D001792:Blood Platelets / Q000187:drug effects* / Q000201:enzymology / Q000502:physiology; D002318:Cardiovascular Diseases / Q000097:blood* / Q000188:drug therapy; D016861:Cyclooxygenase Inhibitors / Q000008:administration & dosage; D005260:Female; D006801:Humans; D008297:Male; D010975:Platelet Aggregation Inhibitors / Q000008:administration & dosage; D010979:Platelet Function Tests / Q000295:instrumentation / Q000379:methods*
chemical_list: D016861:Cyclooxygenase Inhibitors; D010975:Platelet Aggregation Inhibitors; D001241:Aspirin